[chore] migration of plugin-store (#27506)

Plugin store is gradually migrated from:
- https://plugins-store.test.mattermost.com
to
- https://plugins.releases.mattermost.com

We reflect that change here

Note: Currently both CDN's are working as expected, to facilitate the mgiration. Upon succesfull migration, https://plugins-store.test.mattermost.com will be decomissioned

server/Makefile

@@ -271,8 +271,8 @@ prepackaged-plugins: ## Populate the prepackaged-plugins directory.
 	@echo Downloading prepackaged plugins: $(PLUGIN_PACKAGES)
 	mkdir -p prepackaged_plugins
 	@cd prepackaged_plugins && for plugin_package in $(PLUGIN_PACKAGES) ; do \
-		curl -f -O -L https://plugins-store.test.mattermost.com/release/$$plugin_package.tar.gz; \
-		curl -f -O -L https://plugins-store.test.mattermost.com/release/$$plugin_package.tar.gz.sig; \
+		curl -f -O -L https://plugins.releases.mattermost.com/release/$$plugin_package.tar.gz; \
+		curl -f -O -L https://plugins.releases.mattermost.com/release/$$plugin_package.tar.gz.sig; \
 	done
 
 prepackaged-binaries: ## Populate the prepackaged-binaries to the bin directory