drop non-null assertion in retry loop

Flip the order of the response/error check so TypeScript narrows the
types itself rather than relying on `response!` to assert what the code
already guarantees by construction.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Fredrik Adelöw <freben@spotify.com>

packages/integration/src/gitlab/GitLabIntegration.ts

@@ -130,8 +130,8 @@ export class GitLabIntegration implements ScmIntegration {
 
         // Out of attempts: surface the response or rethrow the captured error
         if (attempt++ >= maxRetries) {
-          if (error) throw error;
-          return response!;
+          if (response) return response;
+          throw error;
         }
 
         // Determine delay from Retry-After header if present, otherwise exponential backoff