[doxygen] Fix bad doxygen results for BugReporterVisitors.h

`{@code xxxxx}` triggers a Doxygen bug. The bug may be matching the
close brace with the open brace of the namespace
declaration (`namespace clang {` or `namespace ento {`).

Differential Revision: https://reviews.llvm.org/D85105

clang/include/clang/StaticAnalyzer/Core/BugReporter/BugReporterVisitors.h

@@ -53,7 +53,7 @@ public:
   /// Note that this function does *not* get run on the very last node
   /// of the report, as the PathDiagnosticPiece associated with the
   /// last node should be unique.
-  /// Use {@code getEndPath} to customize the note associated with the report
+  /// Use \ref getEndPath to customize the note associated with the report
   /// end instead.
   ///
   /// The last parameter can be used to register a new visitor with the given