Remove project from grafana url placeholder

What does this MR do?

We have a Grafana integration on the Settings >> Operations page. This includes a field for the Grafana server.

The placeholder on this field incorrectly included the project section of the url. This MR removes the project selection to fix the issue.

Note: This feature is currently behind a feature flag.

Issue: #31376 (closed)

Screenshots

before	after

Does this MR meet the acceptance criteria?

Conformity

• [n/a] Changelog entry Not required as feature is unreleased and behind feature flag
• Documentation (if required) docs MR here !18541 (merged)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [n/a] Database guides
• [n/a] 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

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:

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