Revert "[InstCombine] Optimise x / sqrt(y / z) with fast-math pattern. (#76737)"

This reverts commit bb5c3899.

That commit caused failed asserts like this:

$ cat repro.c
float a, b;
double sqrt();
void c() { b = a / sqrt(a); }
$ clang -target x86_64-linux-gnu -c -O2 -ffast-math repro.c
clang: ../lib/IR/Instruction.cpp:522: bool llvm::Instruction::hasAllowReassoc() const: Assertion `isa<FPMathOperator>(this) && "getting fast-math flag on invalid op"' failed.