Revert "implemented labeler which automatically adds RPC label to anything modifying RPC files (#3499)" (#3517)

This reverts commit fe98b81b80.

.github/labeler.yml

@@ -1,4 +0,0 @@
-# Add 'RPC' to any changes within 'src/rpc/*' or 'src/wallet/rpc*'
-RPC:
-  - src/rpc/*
-  - src/wallet/rpc*

.github/workflows/label.yml

@@ -1,19 +0,0 @@
-# This workflow will triage pull requests and apply a label based on the
-# paths that are modified in the pull request.
-#
-# To use this workflow, you will need to set up a .github/labeler.yml
-# file with configuration.  For more information, see:
-# https://github.com/actions/labeler/blob/master/README.md
-
-name: Labeler
-on: [pull_request]
-
-jobs:
-  label:
-
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/labeler@v2
-        with:
-          repo-token: "${{ secrets.GITHUB_TOKEN }}"