fix(ci): add end anchor to SemVer regex in artifacthub validation

The regex `^\d+\.\d+\.\d+` was missing a `$` end anchor, allowing
versions like `1.2.3.4` or `1.2.3extra` to pass validation.

Fixed to `^\d+\.\d+\.\d+$` for strict X.Y.Z matching.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/plugin-ci.yaml

@@ -48,7 +48,7 @@ jobs:
 
           # Version must be SemVer
           version = pkg.get("version", "")
-          if version and not re.match(r'^\d+\.\d+\.\d+', str(version)):
+          if version and not re.match(r'^\d+\.\d+\.\d+$', str(version)):
               errors.append(f"version '{version}' is not SemVer (expected X.Y.Z)")
 
           # Headlamp plugin annotations