Only run code coverage report on non-fork branches (#3571)

- **PR Description**

Codacy's coverage report feature requires the use of a secret key, which
is only available on the main repo and is not available on forks. So,
the step has been always failing on any forks. This commit ensures that
we only run it on non-forks.

This greatly diminishes the value of the coverage reports. I've talked
to one of the Codacy people and advised that they should just have an
API key for coverage reports which is not a secret, like what bugsnag
does.

I've disabled the gate in codacy meaning if the coverage ever drops
beneath some percentage, the job won't fail. It wouldn't make sense to
fail the job if some other PR from a fork was responsible for reducing
the coverage percentage beneath some threshold.

- **Please check if the PR fulfills these requirements**

* [ ] Cheatsheets are up-to-date (run `go generate ./...`)
* [ ] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [ ] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] Docs (specifically `docs/Config.md`) have been updated if
necessary
* [ ] You've read through your own file changes for silly mistakes etc

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.github/workflows/ci.yml

@@ -188,6 +188,7 @@ jobs:
   upload-coverage:
     # List all jobs that produce coverage files
     needs: [unit-tests, integration-tests]
+    if: github.event.repository.fork == false
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code