build: Rename md5 to checksums as part of .PHONY target

In commit 46d03d37bf3a75e86f9f8ab56c6a939d04f23383 I renamed a Makefile target
from md5 to checksums, (as we switched from MD5 checksums to SHA-256
checksums, so the more general name is more future proof).

But that commit missed one mention of "md5" as a dependency of the .PHONY
target. Rename that here as well.
1 file changed