ci: set retention-days on platform binary artifacts in build job

The seven cross-platform binaries were using GitHub's default 90-day
retention. Cluster-log artifacts in the same file already use 7 days.
Setting 30 days on binaries aligns retention with a reasonable policy
and prevents unbounded storage accumulation.

Author: Ankitsinghsisodya

.github/workflows/functions.yaml

@@ -473,30 +473,37 @@ jobs:
         with:
           name: OSX Binary (AMD)
           path: func_darwin_amd64
+          retention-days: 30
       - uses: actions/upload-artifact@v4
         with:
           name: OSX Binary (ARM)
           path: func_darwin_arm64
+          retention-days: 30
       - uses: actions/upload-artifact@v4
         with:
           name: Linux Binary (AMD)
           path: func_linux_amd64
+          retention-days: 30
       - uses: actions/upload-artifact@v4
         with:
           name: Linux Binary (ARM)
           path: func_linux_arm64
+          retention-days: 30
       - uses: actions/upload-artifact@v4
         with:
           name: Linux Binary (PPC64LE)
           path: func_linux_ppc64le
+          retention-days: 30
       - uses: actions/upload-artifact@v4
         with:
           name: Linux Binary (S390X)
           path: func_linux_s390x
+          retention-days: 30
       - uses: actions/upload-artifact@v4
         with:
           name: Windows Binary
           path: func_windows_amd64.exe
+          retention-days: 30
 
   publish-utils-image:
     name: Publish Utils Image