Fix erroneous change directory for Gitpod

What does this MR do?

This MR fixes an issue when initialising Gitpod failed to run gdk stop because it wasn't in the correct directory:

Before

--snip--
Wed 27 Jan 2021 08:36:06 AM UTC – Stopping GDK

The current working directory is not inside a gitlab-development-kit
installation. Use 'cd' to go to your gitlab-development-kit or create
a new one with 'gdk init'.

gdk init [DIRECTORY] # Default: /workspace/gitlab/gitlab-development-kit

Wed 27 Jan 2021 08:36:08 AM UTC – GDK stopped
--snip--

After

--snip--
Wed 27 Jan 2021 10:52:04 AM UTC – Stopping GDK
ℹ️  gdk stop: before hook -> cd gitlab && bin/spring stop || true
Spring is not running
=> Shutting down all services: 
ok: down: ./services/gitlab-pages: 220s
ok: down: ./services/gitlab-workhorse: 220s
ok: down: ./services/jaeger: 220s
ok: down: ./services/rails-background-jobs: 220s
ok: down: ./services/rails-web: 220s
ok: down: ./services/webpack: 220s
ok: down: ./services/praefect: 0s
ok: down: ./services/redis: 0s
ok: down: ./services/praefect-gitaly-0: 1s
ok: down: ./services/postgresql: 0s
=> Shutting down runsvdir (pid 9493)

✅️ All services have been shut down!
Wed 27 Jan 2021 10:52:19 AM UTC – GDK stopped
--snip--

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team