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
diff --git a/libc/platform/bionic/mte.h b/libc/platform/bionic/mte.h
index 1e393eb..b11b1a6 100644
--- a/libc/platform/bionic/mte.h
+++ b/libc/platform/bionic/mte.h
@@ -29,10 +29,9 @@
 #pragma once
 
 #include <sys/auxv.h>
-#include <bionic/mte_kernel.h>
 
 inline bool mte_supported() {
-#if defined(__aarch64__) && defined(ANDROID_EXPERIMENTAL_MTE)
+#if defined(__aarch64__)
   static bool supported = getauxval(AT_HWCAP2) & HWCAP2_MTE;
 #else
   static bool supported = false;