[cc] Remove deprecated clang flag for auto-var-init

Bug: http://b/259559364
Bug: http://b/267819531

The extra flag is no longer needed by the scan-deps used by RBE.

Test: `USE_RBE m`
Change-Id: Ia35b78f7b28f9008479256d9fead253910627254
diff --git a/cc/config/global.go b/cc/config/global.go
index 20298dd..835fa46 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -360,14 +360,14 @@
 		// Automatically initialize any uninitialized stack variables.
 		// Prefer zero-init if multiple options are set.
 		if ctx.Config().IsEnvTrue("AUTO_ZERO_INITIALIZE") {
-			flags = append(flags, "-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang -Wno-unused-command-line-argument")
+			flags = append(flags, "-ftrivial-auto-var-init=zero")
 		} else if ctx.Config().IsEnvTrue("AUTO_PATTERN_INITIALIZE") {
 			flags = append(flags, "-ftrivial-auto-var-init=pattern")
 		} else if ctx.Config().IsEnvTrue("AUTO_UNINITIALIZE") {
 			flags = append(flags, "-ftrivial-auto-var-init=uninitialized")
 		} else {
 			// Default to zero initialization.
-			flags = append(flags, "-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang -Wno-unused-command-line-argument")
+			flags = append(flags, "-ftrivial-auto-var-init=zero")
 		}
 
 		// Workaround for ccache with clang.