[-Wunsafe-buffer-usage] To disable a test on Windows systems.

One of the tests in the commit
'bdf4f2bea50e87f5b9273e3bbc9a7753bca3a6bb' sometimes fails on one of
the buildbots runing on a Windows machine. For example,
"https://lab.llvm.org/buildbot/#/builders/60/builds/10615" is a failed
build.

Now we disable it until we figure out why this could happen.

Author: ziqingluo-90

clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-local-var-span.cpp

@@ -1,3 +1,4 @@
+// REQUIRES: !system-windows
 // RUN: %clang_cc1 -std=c++20 -Wunsafe-buffer-usage -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
 typedef int * Int_ptr_t;
 typedef int Int_t;
@@ -97,10 +98,10 @@ void decl_without_init() {
   int tmp;
   int * p;
   // CHECK-DAG: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:10}:"std::span<int> p"
-  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-2]]
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-2]]:{{^3}}
   Int_ptr_t q;
   // CHECK-DAG: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:14}:"std::span<int> q"
-  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-2]]
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-2]]:{{^3}}
   tmp = p[5];
   tmp = q[5];
 }