index: Add Serial Modem v2.0.0-preview1 and remove v0.3.0 (#113)

Update Serial Modem releases.

Signed-off-by: Tommi Rantanen <tommi.rantanen@nordicsemi.no>

Author: trantanen

index/nrfconnect.json

@@ -279,6 +279,12 @@
       "avatar": "https://avatars.githubusercontent.com/u/40860733?s=200&v=4",
       "docsUrl": "https://docs.nordicsemi.com/bundle/addon-serial_modem-latest/page/index.html",
       "releases": [
+        {
+          "tag": "v2.0.0-preview1",
+          "name": "Serial Modem v2.0.0-preview1",
+          "date": "2026-04-10T00:00:00Z",
+          "sdk": "v3.3.0-rc1"
+        },
         {
           "tag": "v1.0.1",
           "name": "Serial Modem v1.0.1",
@@ -290,12 +296,6 @@
           "name": "Serial Modem v1.0.0",
           "date": "2026-02-19T00:00:00Z",
           "sdk": "v3.2.2"
-        },
-        {
-          "tag": "v0.3.0",
-          "name": "Serial Modem v0.3.0",
-          "date": "2025-12-18T00:00:00Z",
-          "sdk": "v3.2.0"
         }
       ],
       "defaultBranch": "v1.0.1"