Brew untap hashicorp

`brew test-bot` eventually walks all formulae to determine what might
depend on cbmc-viewer, thereby walking into what appears to be a broken
formula at `hashicorp/tap/vagrant`. This tap is entirely unrelated and
also unnecessary for our purposes, so just remove it.

Author: tautschnig

.github/workflows/release-brew.yaml

@@ -116,6 +116,7 @@ jobs:
       - name: Checkout PR
         run: |
           brew tap ${{ env.TAP }}
+          brew untap --force hashicorp/tap
           brew update-reset
           cd $(brew --repo ${{ env.TAP }})
           git remote add fork-repo ${{ env.FORK_REPO }}