fix: plugins/explore/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-QS-15268416

Author: snyk-io[bot]

plugins/explore/package.json

@@ -40,7 +40,7 @@
     "@backstage/plugin-explore-common": "workspace:^",
     "@backstage/plugin-explore-react": "workspace:^",
     "@backstage/plugin-search-common": "workspace:^",
-    "@backstage/plugin-search-react": "workspace:^",
+    "@backstage/plugin-search-react": "0.1.0",
     "@backstage/theme": "workspace:^",
     "@material-ui/core": "^4.12.2",
     "@material-ui/icons": "^4.9.1",