[Attributor][NFC] Fix indentation

Summary: The patch D81022 seems to break the indentation of the `cleanupIR()` function. This patch fixes this problem

Reviewers: jdoerfert, sstefan1, uenoku

Reviewed By: jdoerfert

Subscribers: hiraditya, uenoku, kuter, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D82260