Silence clang-tidy warnings around SkBlockAllocator

Change-Id: I4a825c0d191f3f24d558c4331e07fe2a55832f76
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/441838
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed