[-Wunsafe-buffer-usage] Remove an unnecessary const-qualifier

A follow-up change for 6d861d4:
remove an unnecessary const-qualifier so that the code doesn't have to
remove the qualifier explicitly using `std::remove_const_t`, which
triggers a warning at some bots (e.g.,
https://lab.llvm.org/buildbot/#/builders/247/builds/4442).

clang/include/clang/Sema/AnalysisBasedWarnings.h

@@ -24,7 +24,7 @@ class FunctionDecl;
 class QualType;
 class Sema;
 namespace sema {
-  class FunctionScopeInfo;
+class FunctionScopeInfo;
 }
 
 namespace sema {
@@ -38,6 +38,7 @@ class AnalysisBasedWarnings {
     unsigned enableCheckUnreachable : 1;
     unsigned enableThreadSafetyAnalysis : 1;
     unsigned enableConsumedAnalysis : 1;
+
   public:
     Policy();
     void disableCheckFallThrough() { enableCheckFallThrough = 0; }
@@ -51,7 +52,7 @@ class AnalysisBasedWarnings {
   std::unique_ptr<InterProceduralData> IPData;
 
   enum VisitFlag { NotVisited = 0, Visited = 1, Pending = 2 };
-  llvm::DenseMap<const FunctionDecl*, VisitFlag> VisitedFD;
+  llvm::DenseMap<const FunctionDecl *, VisitFlag> VisitedFD;
 
   /// \name Statistics
   /// @{
@@ -93,11 +94,11 @@ class AnalysisBasedWarnings {
   AnalysisBasedWarnings(Sema &s);
   ~AnalysisBasedWarnings();
 
-  void IssueWarnings(Policy P, FunctionScopeInfo *fscope,
-                     const Decl *D, QualType BlockType);
+  void IssueWarnings(Policy P, FunctionScopeInfo *fscope, const Decl *D,
+                     QualType BlockType);
 
   // Issue warnings that require whole-translation-unit analysis.
-  void IssueWarnings(const TranslationUnitDecl *D);
+  void IssueWarnings(TranslationUnitDecl *D);
 
   Policy getDefaultPolicy() { return DefaultPolicy; }