Completely remove Project Browser integration

Closes #3508067

.tugboat/config.yml

@@ -30,8 +30,6 @@ services:
         composer require 'drupal/gin_login:^2.1'
         # Require Admin Toolbar
         composer require 'drupal/admin_toolbar:^3.0'
-        # Require Project Browser
-        composer require 'drupal/project_browser:^1.0@beta'
         # Now we can require Gin, specifing the branch name we created
         # above that uses the $TUGBOAT_REPO_ID environment variable.
         composer require drupal/gin:dev-$TUGBOAT_REPO_ID
@@ -57,8 +55,6 @@ services:
         vendor/bin/drush --yes en gin_toolbar
         # Enable gin_login Module.
         vendor/bin/drush --yes en gin_login
-        # Enable project_browser Module.
-        vendor/bin/drush --yes en project_browser
       build: |
         set -eux
         # Delete and re-check out this branch in case this is built from a Base Preview.