Fix the placeholder to "true"

Author: steakhal

clang/test/Analysis/live-stmts.cpp

@@ -1,5 +1,5 @@
 // Disabling this flaky test, see https://github.com/llvm/llvm-project/pull/126913#issuecomment-2655850766
-// UNSUPPORTED: *
+// UNSUPPORTED: true
 
 // RUN: %clang_analyze_cc1 -w -analyzer-checker=debug.DumpLiveExprs %s 2>&1\
 // RUN:   | FileCheck %s