.github/workflows: delete flaky windows-race.yml

It flakes more often than it runs. It provides no value and builds
failure blindness, making people get used to submitting on red.

Bye.

Change-Id: If5491c70737b4c9851c103733b1855af2a90a9e9
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

.github/workflows/windows-race.yml

@@ -1,77 +0,0 @@
-name: Windows race
-
-on:
-  push:
-    branches:
-      - main
-  pull_request:
-    branches:
-      - '*'
-
-jobs:
-  test:
-    runs-on: windows-latest
-
-    if: "!contains(github.event.head_commit.message, '[ci skip]')"
-
-    steps:
-
-    - name: Install Go
-      uses: actions/setup-go@v3
-      with:
-        go-version: 1.19.x
-
-    - name: Checkout code
-      uses: actions/checkout@v3
-
-    - name: Restore Cache
-      uses: actions/cache@v3
-      with:
-        # Note: unlike some other setups, this is only grabbing the mod download
-        # cache, rather than the whole mod directory, as the download cache
-        # contains zips that can be unpacked in parallel faster than they can be
-        # fetched and extracted by tar
-        path: |
-          ~/go/pkg/mod/cache
-          ~\AppData\Local\go-build
-
-        # The -2- here should be incremented when the scheme of data to be
-        # cached changes (e.g. path above changes).
-        # The -race- here ensures that non-race builds and race builds do not
-        # overwrite each others cache, as while they share some files, they
-        # differ in most by volume (build cache).
-        # TODO(raggi): add a go version here.
-        key: ${{ runner.os }}-go-2-race-${{ hashFiles('**/go.sum') }}
-
-    - name: Print toolchain details
-      run: gcc -v
-
-    # There is currently an issue in the race detector in Go on Windows when
-    # used with a newer version of GCC.
-    # See https://github.com/tailscale/tailscale/issues/4926.
-    - name: Downgrade MinGW
-      shell: bash
-      run: |
-        choco install mingw --version 10.2.0 --allow-downgrade
-
-    - name: Test with -race flag
-      # Don't use -bench=. -benchtime=1x.
-      # Somewhere in the layers (powershell?)
-      # the equals signs cause great confusion.
-      run: go test -race -bench . -benchtime 1x ./...
-
-    - uses: k0kubun/action-slack@v2.0.0
-      with:
-        payload: |
-          {
-            "attachments": [{
-              "text": "${{ job.status }}: ${{ github.workflow }} <https://github.com/${{ github.repository }}/commit/${{ github.sha }}/checks|${{ env.COMMIT_DATE }} #${{ env.COMMIT_NUMBER_OF_DAY }}> " +
-                      "(<https://github.com/${{ github.repository }}/commit/${{ github.sha }}|" + "${{ github.sha }}".substring(0, 10) + ">) " +
-                      "of ${{ github.repository }}@" + "${{ github.ref }}".split('/').reverse()[0] + " by ${{ github.event.head_commit.committer.name }}",
-              "color": "danger"
-            }]
-          }
-      env:
-        SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK_URL }}
-      if: failure() && github.event_name == 'push'
-