[updatecli] Bump Fleet version used within installation documentation to 0.12.1

[rancherbot]

INSTALLATION.YAML

Update Fleet CRD asset URL

1 file(s) updated with "https://github.com/rancher/fleet/releases/download/v0.12.1/fleet-crd-0.12.1.tgz": * README.md

v0.12.1

## What's Changed
* Ensure same bundle is selected for non-ready status  by @0xavi0 in https://github.com/rancher/fleet/pull/3498
* Delete no longer targeted bundle deployments by @0xavi0 in https://github.com/rancher/fleet/pull/3511
* Support strict host key checks by @weyfonk in https://github.com/rancher/fleet/pull/3524
* Add Lifecycle Secrets by @manno in https://github.com/rancher/fleet/pull/3528
* Avoid nil pointer dereference reading leader-election options  by @aruiz14 in https://github.com/rancher/fleet/pull/3536
* Prevent panic when fetching latest commit by @weyfonk in https://github.com/rancher/fleet/pull/3539
* Fix resource.PerClusterState incompatibility by @aruiz14 in https://github.com/rancher/fleet/pull/3542
* Bump Go toolchain version to 1.23.8 by @thardeck in https://github.com/rancher/fleet/pull/3544


**Full Changelog**: https://github.com/rancher/fleet/compare/v0.12.0...v0.12.1

Update Fleet asset URL

1 file(s) updated with "https://github.com/rancher/fleet/releases/download/v0.12.1/fleet-0.12.1.tgz": * README.md

v0.12.1

## What's Changed
* Ensure same bundle is selected for non-ready status  by @0xavi0 in https://github.com/rancher/fleet/pull/3498
* Delete no longer targeted bundle deployments by @0xavi0 in https://github.com/rancher/fleet/pull/3511
* Support strict host key checks by @weyfonk in https://github.com/rancher/fleet/pull/3524
* Add Lifecycle Secrets by @manno in https://github.com/rancher/fleet/pull/3528
* Avoid nil pointer dereference reading leader-election options  by @aruiz14 in https://github.com/rancher/fleet/pull/3536
* Prevent panic when fetching latest commit by @weyfonk in https://github.com/rancher/fleet/pull/3539
* Fix resource.PerClusterState incompatibility by @aruiz14 in https://github.com/rancher/fleet/pull/3542
* Bump Go toolchain version to 1.23.8 by @thardeck in https://github.com/rancher/fleet/pull/3544


**Full Changelog**: https://github.com/rancher/fleet/compare/v0.12.0...v0.12.1

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