Meta: Disable "readability-identifier-length" clang-tidy checks

Short identifier names like "i", "x", "fd" are fairly common and fine.

.clang-tidy

@@ -33,6 +33,7 @@ Checks: >
  -performance-noexcept-move-constructor,
  -performance-no-int-to-ptr,
  -readability-braces-around-statements,
+ -readability-identifier-length,
  -readability-magic-numbers,
  -readability-named-parameter,
  -readability-uppercase-literal-suffix,