fix(tools): ignore the .git folder when checking for copyright header

[syhol]

When running deno task ok recently I found that it failed the fmt:licence-headers section because a recent new branch has been created https://github.com/denoland/deno_std/tree/remove-types.d.ts and the check mistakes the remote ref file as a typescript file.

❯ deno task ok
Task ok deno task lint && deno fmt --check && deno task test:browser && deno task test
Task lint deno lint && deno task fmt:licence-headers --check && deno task lint:deprecations && deno task lint:doc-imports && deno task lint:circular && deno task lint:tools-types
Checked 849 files
Task fmt:licence-headers deno run --allow-read --allow-write ./_tools/check_licence.ts "--check"
Missing copyright header: /Users/simon.holloway/Code/deno_std/.git/logs/refs/remotes/upstream/remove-types.d.ts
Missing copyright header: /Users/simon.holloway/Code/deno_std/.git/refs/remotes/upstream/remove-types.d.ts
Copyright header should be "// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license."

After adding .git to the list of folders excluded from this check, deno task ok now passes as expected:

❯ deno task ok                         
Task ok deno task lint && deno fmt --check && deno task test:browser && deno task test
Task lint deno lint && deno task fmt:licence-headers --check && deno task lint:deprecations && deno task lint:doc-imports && deno task lint:circular && deno task lint:tools-types
Checked 849 files
Task fmt:licence-headers deno run --allow-read --allow-write ./_tools/check_licence.ts "--check"
Task lint:deprecations deno run --allow-read --allow-net --allow-env=HOME ./_tools/check_deprecation.ts
Task lint:doc-imports deno run --allow-env --allow-read ./_tools/check_doc_imports.ts
Checked 907 files
Task lint:circular deno run --allow-env --allow-read --allow-net=deno.land ./_tools/check_circular_submodule_dependencies.ts
...

[CLAassistant]

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[iuioiua]

Nice catch! Thank you.