Update plugins/catalog-backend-module-gitlab/src/lib/client.ts

Apply suggestion

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Signed-off-by: sbarrypoppulo <101636916+sbarrypoppulo@users.noreply.github.com>

plugins/catalog-backend-module-gitlab/src/lib/client.ts

@@ -187,7 +187,7 @@ export class GitLabClient {
           method: 'POST',
           headers: {
             ...getGitLabRequestOptions(this.config).headers,
-            ['Content-Type']: 'application/json',
+            'Content-Type': 'application/json',
           },
           body: JSON.stringify({
             variables: { group: groupPath, relations: relations, endCursor },