fix(plugins): drop unused gitBranch re-export from the package entry

@trigger.dev/plugins re-exported sanitizeBranchName/isValidGitBranchName
from @trigger.dev/core purely as a convenience forwarder. Nothing imports
them through this package — every consumer imports them directly from
@trigger.dev/core/v3/utils/gitBranch. Removing the forwarder keeps the
package entry free of runtime core imports, so consumers that bundle it
from source don't drag an unrelated core subpath into their build.

Author: matt-aitken

packages/plugins/src/index.ts

@@ -18,8 +18,3 @@ export type {
 } from "./rbac.js";
 
 export { buildJwtAbility } from "./rbac.js";
-
-// Convenience re-exports — give plugin authors one import surface
-// without reaching into @trigger.dev/core directly. Both helpers live in
-// core; this is purely a forwarder.
-export { sanitizeBranchName, isValidGitBranchName } from "@trigger.dev/core/v3/utils/gitBranch";