[NFC][llvm-reduce] Purify for_each usage in Operand Bundles into range-based for loop

Summary:
As per lengthy/heated disscussion in D83351,
and CodingStandards D83431.

Reviewers: dblaikie, nickdesaulniers

Reviewed By: nickdesaulniers

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83434