Correct the attribute spelling for guarded_var and pt_guarded_var.

Patch by Roman Lebedev.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302419 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ThreadSafetyAnalysis.rst

@@ -884,11 +884,11 @@ implementation.
 
   // Deprecated.
   #define PT_GUARDED_VAR \
-    THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded)
+    THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_var)
 
   // Deprecated.
   #define GUARDED_VAR \
-    THREAD_ANNOTATION_ATTRIBUTE__(guarded)
+    THREAD_ANNOTATION_ATTRIBUTE__(guarded_var)
 
   // Replaced by REQUIRES
   #define EXCLUSIVE_LOCKS_REQUIRED(...) \