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

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-WEBPACKDEVSERVER-10300775
- https://snyk.io/vuln/SNYK-JS-WEBPACKDEVSERVER-10300777

Author: snyk-io[bot]

plugins/kafka/package.json

@@ -27,7 +27,7 @@
     "@backstage/catalog-model": "workspace:^",
     "@backstage/config": "workspace:^",
     "@backstage/core-components": "workspace:^",
-    "@backstage/core-plugin-api": "workspace:^",
+    "@backstage/core-plugin-api": "0.1.0",
     "@backstage/plugin-catalog-react": "workspace:^",
     "@backstage/theme": "workspace:^",
     "@material-ui/core": "^4.12.2",