Revert "Reapply "[analyzer] Accept C library functions from the `std` namespace""

This reverts commit e48d5a83.

Fails to build on x86-64 w/gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)
with the following message:

../llvm-project/clang/unittests/StaticAnalyzer/IsCLibraryFunctionTest.cpp:41:28: error: declaration of ‘std::unique_ptr<clang::ASTUnit> IsCLibraryFunctionTest::ASTUnit’ changes meaning of ‘ASTUnit’ [-fpermissive]
   41 |   std::unique_ptr<ASTUnit> ASTUnit;
      |                            ^~~~~~~
In file included from ../llvm-project/clang/unittests/StaticAnalyzer/IsCLibraryFunctionTest.cpp:4:
../llvm-project/clang/include/clang/Frontend/ASTUnit.h:89:7: note: ‘ASTUnit’ declared here as ‘class clang::ASTUnit’
   89 | class ASTUnit {
      |       ^~~~~~~