Add blockedMarketplaces to enterprise managed settings

Add support for blockedMarketplaces in enterprise managed settings,
allowing administrators to prevent specific plugin marketplaces from
being installed. This takes precedence over other marketplace settings.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## 2.0.71
 
+- Added `blockedMarketplaces` to enterprise managed settings, allowing administrators to prevent specific plugin marketplaces from being installed
 - Added /config toggle to enable/disable prompt suggestions
 - Added `/settings` as an alias for the `/config` command
 - Fixed @ file reference suggestions incorrectly triggering when cursor is in the middle of a path