Also changes clang-format SeparateDefinitionBlocks to Leave on ObjC
files, which avoid having an empty new line after API_AVAIABLE and the
declaration.
8dd20dfd33 introduced an explicit check
for the available macOS SDK, meaning that we can be sure that the macOS
13.1 SDK is available. As such, we do not require ifdef guards for the
availability of functions that are older than 13.1.