MM-51792 Replace Boards feature flag with env var (#22739)

* remove Boards feature flag from server, makefile, and docker

* Update server/boards/server/boards_service_util.go

Co-authored-by: Miguel de la Cruz <miguel@mcrx.me>

---------

Co-authored-by: Miguel de la Cruz <miguel@mcrx.me>

server/channels/app/product.go

@@ -72,14 +72,14 @@ func (s *Server) initializeProducts(
 
 func (s *Server) shouldStart(product string) bool {
 	if product == "boards" {
-		if !s.Config().FeatureFlags.BoardsProduct {
-			s.Log().Warn("Skipping boards start: not enabled via feature flag")
+		if os.Getenv("MM_DISABLE_BOARDS") == "true" {
+			s.Log().Warn("Skipping Boards start: disabled via env var")
 			return false
 		}
 	}
 	if product == "playbooks" {
 		if os.Getenv("MM_DISABLE_PLAYBOOKS") == "true" {
-			s.Log().Warn("Skipping playbooks start: disabled via env var")
+			s.Log().Warn("Skipping Playbooks start: disabled via env var")
 			return false
 		}
 	}