[clang][llvm][NFC] Change misexpect's tolerance option to be 32-bit

In D131869 we noticed that we jump through some hoops because we parse the
tolerance option used in MisExpect.cpp into a 64-bit integer. This is
unnecessary, since the value can only be in the range [0, 100).

This patch changes the underlying type to be 32-bit from where it is
parsed in Clang through to it's use in LLVM.

Reviewed By: jloser

Differential Revision: https://reviews.llvm.org/D131935