Update source_code.py to allow self-hosted GitLab for code references (…

…dagster-io#23160)

## Summary & Motivation

Currently the git [code
reference](https://docs.dagster.io/guides/dagster/code-references#in-any-dagster-environment)
feature only works for URLs containing "gitlab.com" and "github.com".
This doesn't work with self-hosted GitLab because the string
"gitlab.com" is not in "gitlab.self-hosted.xyz".

dagster-io#23135

## How I Tested These Changes

Confirmed locally against self-hosted GitLab instance.

python_modules/dagster/dagster/_core/definitions/metadata/source_code.py

@@ -313,7 +313,7 @@ def link_code_references_to_git(
  )
  )
  """
- if "gitlab.com" in git_url:
+ if "gitlab" in git_url:
  git_url = _build_gitlab_url(git_url, git_branch)
  elif "github.com" in git_url:
  git_url = _build_github_url(git_url, git_branch)