deps: revert linting to older version due to broken lint rule (#36336)

## Description

<!-- Describe the goal and purpose of this PR. -->

The ESLint plugin was broken. There's a fix for it but it's not released
yet:
testing-library/eslint-plugin-testing-library#1048

## Checklist

<!--- Please delete options that are not relevant. Boxes should be
checked by reviewer. -->
- [ ] Enable backports when necessary (fex. [for bug
fixes](https://github.com/camunda/camunda/blob/main/CONTRIBUTING.md#backporting-changes)
or [for CI
changes](https://github.com/camunda/camunda/wiki/CI-&-Automation#when-to-backport-ci-changes)).

## Related issues

closes #

Author: georgios-goulos

operate/client/package-lock.json

@@ -96,7 +96,7 @@
     "eslint-plugin-prettier": "5.5.1",
     "eslint-plugin-react-hooks": "5.2.0",
     "eslint-plugin-react-refresh": "0.4.20",
-    "eslint-plugin-testing-library": "7.6.3",
+    "eslint-plugin-testing-library": "7.5.3",
     "globals": "16.3.0",
     "jsdom": "26.1.0",
     "monaco-editor": "0.52.2",

operate/client/package.json

@@ -96,7 +96,7 @@
     "eslint-plugin-prettier": "5.5.0",
     "eslint-plugin-react-hooks": "5.2.0",
     "eslint-plugin-react-refresh": "0.4.20",
-    "eslint-plugin-testing-library": "7.6.3",
+    "eslint-plugin-testing-library": "7.5.3",
     "jsdom": "26.1.0",
     "monaco-editor": "0.52.2",
     "msw": "2.10.2",