feat(github-enterprise): Route installation_repositories to control silo

[wedamija]

Remove the should_route_to_control_silo override in GithubEnterpriseRequestParser so it inherits the parent's routing, which sends installation_repositories events to control silo.

We do this to make sure the webhooks for GHE will also route to the right place

[sentry]

Bug: Removing the should_route_to_control_silo override routes installation_repositories webhooks for GHE, but the GitHubEnterpriseWebhookEndpoint lacks a handler, causing these events to be silently dropped.
_{Severity: HIGH}

Suggested Fix

Implement a GitHubEnterpriseInstallationRepositoriesEventWebhook handler, similar to the existing InstallationRepositoriesEventWebhook for regular GitHub. Register this new handler in the _handlers dictionary within GitHubEnterpriseWebhookEndpoint for the GithubWebhookType.INSTALLATION_REPOSITORIES event type. This will ensure that repository changes for GitHub Enterprise installations are processed correctly.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: src/sentry/middleware/integrations/parsers/github_enterprise.py#L18-L23

Potential issue: The pull request removes an override in
`GithubEnterpriseRequestParser`, causing it to inherit the parent's behavior of routing
`installation_repositories` webhooks to the control silo. However, the
`GitHubEnterpriseWebhookEndpoint` does not have a handler registered for this event
type. As a result, when a GitHub Enterprise instance sends an
`installation_repositories` webhook, the endpoint's `_handle` method will find no
handler and silently return a `204` status. This prevents the necessary repository
synchronization tasks from running when repositories are added to or removed from a GHE
app installation.

_{Did we get this right? 👍 / 👎 to inform future reviews.}