Delete lgtm.yml

This doesn't seem to be working, so removing for the minute.

.github/workflows/lgtm.yml

@@ -1,23 +0,0 @@
-name: LGTM Reaction
-on:
-  pull_request_review:
-    types: [submitted]
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@1.0.0
-      - uses: micnncim/action-lgtm-reaction@v0.5.4
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          GITHUB_REPOSITORY: ${{ github.repository }}
-          GITHUB_ISSUE_NUMBER: ${{ github.event.issue.number }}
-          GITHUB_COMMENT_BODY: ${{ github.event.comment.body }}
-          GITHUB_COMMENT_ID: ${{ github.event.comment.id }}
-          GITHUB_PULL_REQUEST_NUMBER: ${{ github.event.pull_request.number }}
-          GITHUB_REVIEW_BODY: ${{ github.event.review.body }}
-          GITHUB_REVIEW_ID: ${{ github.event.review.id }}
-        with:
-          trigger: '["^LGTM!?$"]'
-          override: true
-          source: lgtmapp