fix(deps): update dependency postcss-simple-vars to v7

Author: renovate[bot]

package-lock.json

@@ -76,7 +76,7 @@
     "papaparse": "^5.3.0",
     "postcss-import": "^12.0.0",
     "postcss-loader": "4.3.0",
-    "postcss-simple-vars": "^5.0.1",
+    "postcss-simple-vars": "^7.0.0",
     "prop-types": "^15.5.10",
     "query-string": "^5.1.1",
     "raw-loader": "^4.0.0",