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

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-TAR-15032660
- https://snyk.io/vuln/SNYK-JS-TAR-15127355
- https://snyk.io/vuln/SNYK-JS-DIFF-14917201
- https://snyk.io/vuln/SNYK-JS-ESLINT-15102420

Author: snyk-bot

plugins/periskop/package.json

@@ -24,11 +24,11 @@
   },
   "dependencies": {
     "@backstage/catalog-model": "workspace:^",
-    "@backstage/core-components": "workspace:^",
+    "@backstage/core-components": "0.8.6",
     "@backstage/core-plugin-api": "workspace:^",
     "@backstage/errors": "workspace:^",
     "@backstage/plugin-catalog-react": "workspace:^",
-    "@backstage/theme": "workspace:^",
+    "@backstage/theme": "0.1.1",
     "@material-ui/core": "^4.12.2",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.61",