fix: plugins/techdocs-addons-test-utils/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-AJV-15274295

Author: snyk-io[bot]

plugins/techdocs-addons-test-utils/package.json

@@ -39,7 +39,7 @@
     "@backstage/plugin-catalog": "workspace:^",
     "@backstage/plugin-search-react": "workspace:^",
     "@backstage/plugin-techdocs": "workspace:^",
-    "@backstage/plugin-techdocs-react": "workspace:^",
+    "@backstage/plugin-techdocs-react": "0.1.0",
     "@backstage/test-utils": "workspace:^",
     "@backstage/theme": "workspace:^",
     "@material-ui/core": "^4.12.2",