[Mellanox]Fixing hwsku.son for Mellanox-SN5600-O128 (#22717)

<!--
 Please make sure you've read and understood our contributing guidelines:
 https://github.com/Azure/SONiC/blob/gh-pages/CONTRIBUTING.md

 failure_prs.log skip_prs.log Make sure all your commits include a signature generated with `git commit -s` **

 If this is a bug fix, make sure your description includes "fixes #xxxx", or
 "closes #xxxx" or "resolves #xxxx"

 Please provide the following information:
-->

#### Why I did it
Fixing hwsku.json for Ethernet512 in Mellanox-SN5600-O128

##### Work item tracking
- Microsoft ADO **(number only)**:

#### How I did it
Corrected the breakout mode. Without it the below error is seen

```
sonic-cfggen -H -k Mellanox-SN5600-O128 --preset t1 > /etc/sonic/tmp_cfg.json
Traceback (most recent call last):
 File "/usr/local/bin/sonic-cfggen", line 517, in <module>
 main()
 File "/usr/local/bin/sonic-cfggen", line 363, in main
 (ports, _, _) = get_port_config(hwsku, platform, args.port_config, hwsku_config_file=args.hwsku_config, asic_name=asic_name)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/usr/local/lib/python3.11/dist-packages/portconfig.py", line 207, in get_port_config
 return parse_platform_json_file(hwsku_json_file, port_config_file)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/usr/local/lib/python3.11/dist-packages/portconfig.py", line 425, in parse_platform_json_file
 child_ports = get_child_ports(intf, brkout_mode, platform_json_file)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/usr/local/lib/python3.11/dist-packages/portconfig.py", line 398, in get_child_ports
 mode_handler = BreakoutCfg(interface, breakout_mode, port_dict[INTF_KEY][interface])
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/usr/local/lib/python3.11/dist-packages/portconfig.py", line 323, in __init__
 raise RuntimeError("Unsupported breakout mode {}!".format(bmode))
RuntimeError: Unsupported breakout mode 1x25G(1)[10G]!
```

#### How to verify it

Ran sonic-cfggen command and confirmed it works fine.

<!--
If PR needs to be backported, then the PR must be tested against the base branch and the earliest backport release branch and provide tested image version on these two branches. For example, if the PR is requested for master, 202211 and 202012, then the requester needs to provide test results on master and 202012.
-->

#### Which release branch to backport (provide reason below if selected)

<!--
- Note we only backport fixes to a release branch, *not* features!
- Please also provide a reason for the backporting below.
- e.g.
- [x] 202006
-->

- [ ] 201811
- [ ] 201911
- [ ] 202006
- [ ] 202012
- [ ] 202106
- [ ] 202111
- [ ] 202205
- [ ] 202211
- [ ] 202305

#### Tested branch (Please provide the tested image version)

<!--
- Please provide tested image version
- e.g.
- [x] 20201231.100
-->

- [ ] <!-- image version 1 -->
- [ ] <!-- image version 2 -->

#### Description for the changelog
<!--
Write a short (one line) summary that describes the changes in this
pull request for inclusion in the changelog:
-->

<!--
 Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.
-->

#### Link to config_db schema for YANG module changes
<!--
Provide a link to config_db schema for the table for which YANG model
is defined
Link should point to correct section on https://github.com/Azure/sonic-buildimage/blob/master/src/sonic-yang-models/doc/Configuration.md
-->

#### A picture of a cute animal (not mandatory but encouraged)

Author: mssonicbld

device/mellanox/x86_64-nvidia_sn5600-r0/Mellanox-SN5600-O128/hwsku.json

@@ -385,7 +385,7 @@
             "default_brkout_mode": "2x400G[200G,100G,50G,40G,25G,10G]"
         },
         "Ethernet512": {
-            "default_brkout_mode": "1x25G(1)[10G]"
+            "default_brkout_mode": "1x25G[10G]"
         }
     }
 }