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>

model/feature_flags.go

@@ -51,9 +51,6 @@ type FeatureFlags struct {
 
 	CommandPalette bool
 
-	// Enable Boards as a product (multi-product architecture)
-	BoardsProduct bool
-
 	// A/B Test on posting a welcome message
 	SendWelcomePost bool
 
@@ -95,7 +92,6 @@ func (f *FeatureFlags) SetDefaults() {
 	f.InsightsEnabled = true
 	f.CommandPalette = false
 	f.CallsEnabled = true
-	f.BoardsProduct = false
 	f.SendWelcomePost = true
 	f.PostPriority = true
 	f.PeopleProduct = false