ghcup metadata gives incorrect dlSubdir of testsuite artifact
As noted in https://github.com/haskell/ghcup-metadata/pull/186#discussion_r1524064965, the dlSubdir
of the testsuite artifact in the generated ghcup metadata is incorrect. It is listed as dlSubdir: ghc-$ver
whereas it should be dlSubdir: ghc-$ver/testsuite
.