.clang-tidy: disable misc-include-cleaner (#2077)

This check was recently added to clang-tidy, but the code base doesn't
quite comply to it, so disable it for now.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@2cea844

Author: svenvh

llvm-spirv/.clang-tidy

@@ -5,6 +5,7 @@ Checks: |
   -llvm-header-guard,
   misc-*,
   -misc-const-correctness,
+  -misc-include-cleaner,
   -misc-no-recursion,
   -misc-non-private-member-variables-in-classes,
   -misc-unused-parameters,
@@ -14,6 +15,7 @@ WarningsAsErrors: |
   -llvm-header-guard,
   misc-*,
   -misc-const-correctness,
+  -misc-include-cleaner,
   -misc-no-recursion,
   -misc-non-private-member-variables-in-classes,
   -misc-unused-parameters,