Remove ANDROID_EXPERIMENTAL_MTE.

Now that the feature guarded by this flag has landed in Linux 5.10
we no longer need the flag, so we can remove it.

Bug: 135772972
Change-Id: I02fa50848cbd0486c23c8a229bb8f1ab5dd5a56f

android/variable.go

@@ -139,10 +139,6 @@ type variableProperties struct {
 			Enabled *bool
 		}
 
-		Experimental_mte struct {
-			Cflags []string `android:"arch_variant"`
-		} `android:"arch_variant"`
-
 		Native_coverage struct {
 			Src          *string  `android:"arch_variant"`
 			Srcs         []string `android:"arch_variant"`
@@ -264,8 +260,6 @@ type productVariables struct {
 
 	DisableScudo *bool `json:",omitempty"`
 
-	Experimental_mte *bool `json:",omitempty"`
-
 	VendorPath    *string `json:",omitempty"`
 	OdmPath       *string `json:",omitempty"`
 	ProductPath   *string `json:",omitempty"`