CTest: drop suppression for gcc 2.9.6 errors from default Valgrind flags

The --workaround-gcc296-bugs has been part of the default Valgrind flags since
Valgrind support was added in commit 5b232ded151fc22144978b74cdaf7031d466e527
(ENH: Add initial memory check support which works for Valgrind, 2003-12-15).
The Valgrind manpage says that this option should be avoided if not really
needed as it may cause real errors to get ignored. If someone uses a compiler
that really needs the flag this flag should be set by the user explicitely.
Most users will never set any flags and probably never notice that they use a
flag they shouldn't.

Source/CTest/cmCTestMemCheckHandler.cxx

@@ -491,7 +491,6 @@ bool cmCTestMemCheckHandler::InitializeMemoryChecking()
         this->MemoryTesterOptions.push_back("--tool=memcheck");
         this->MemoryTesterOptions.push_back("--leak-check=yes");
         this->MemoryTesterOptions.push_back("--show-reachable=yes");
-        this->MemoryTesterOptions.push_back("--workaround-gcc296-bugs=yes");
         this->MemoryTesterOptions.push_back("--num-callers=50");
         }
       if ( this->CTest->GetCTestConfiguration(