fix: Deprecated support for eslint@^6

\### Rationale
No longer effective on `eslint@6`. It does not throw an error but it
does not work either.  Not sure when it happened but likely in `>1.2.4`

package.json

@@ -87,7 +87,7 @@
         "@typescript-eslint/experimental-utils": "^4.32.0"
     },
     "peerDependencies": {
-        "eslint": ">=6.8.0"
+        "eslint": "^7.0.0"
     },
     "resolutions": {
         "trim": "^1.0.1"