build(aio): remove unused script and GitHub token

Since 808bd4af4, we are no longer pre-verifying PRs before uploading the build
artifacts to the preview server, thus we no longer need the
`travis-preverify-pr.sh` script or the `GITHUB_TEAM_MEMBERSHIP_CHECK_KEY`
variable.

aio/aio-builds-setup/docs/misc--integrate-with-ci.md

@@ -3,10 +3,9 @@
 
 TODO (gkalpak): Add docs. Mention:
 - Travis' JWT addon (+ limitations).
-  Relevant files: `.travis.yml`
+  Relevant files: `.travis.yml`, `scripts/ci/env.sh`
 - Testing on CI.
-  Relevant files: `ci/test-aio.sh`, `aio/aio-builds-setup/scripts/test.sh`
-- Preverifying on CI.
-  Relevant files: `ci/deploy.sh`, `aio/aio-builds-setup/scripts/travis-preverify-pr.sh`
+  Relevant files: `scripts/ci/test-aio.sh`, `aio/aio-builds-setup/scripts/test.sh`
 - Deploying from CI.
-  Relevant files: `ci/deploy.sh`, `aio/scripts/deploy-preview.sh`
+  Relevant files: `scripts/ci/deploy.sh`, `aio/scripts/deploy-preview.sh`,
+                  `aio/scripts/deploy-to-firebase.sh`

aio/aio-builds-setup/docs/overview--scripts-and-commands.md

@@ -16,13 +16,6 @@ available:
   Can be used for running the tests for `<aio-builds-setup-dir>/dockerbuild/scripts-js/`. This is
   useful for CI integration. See [here](misc--integrate-with-ci.md) for more info.
 
-- `travis-preverify-pr.sh`:
-  Can be used for "pre-verifying" a PR before uploading the artifacts to the server. It checks
-  whether the author of the PR is a member of one of the specified GitHub teams (therefore allowed
-  to upload build artifacts) or the PR has the specified "trusted PR" label (meaning it has been
-  manually verified by a trusted member). This is useful for CI integration.
-  See [here](misc--integrate-with-ci.md) for more info.
-
 - `update-preview-server.sh`:
   Can be used for updating the docker container (and image) based on the latest changes checked out
   from a git repository. See [here](vm-setup--update-docker-container.md) for more info.