Add proto override for github.com/hashicorp/go-plugin to default_gazelle_overrides.bzl (#2062)

**What type of PR is this?**

Other

**What package or component does this PR mostly affect?**

cmd/gazelle

**What does this PR do? Why is it needed?**

Proto generation must be disabled as github.com/hashicorp/go-plugin is
broken and generated proto bindings are already available in the repo.

**Which issues(s) does this PR fix?**

**Other notes for review**

Co-authored-by: Utkarsh Chanchlani <utkarsh.chanchlani@thoughtspot.com>
1 file changed