fix skips for JS backend

2cb49239 added js_skip(), which calls the skip function. This is wrong because the arguments are supplied by the testrunner. This commit fixes that by passing the function symbol instead of calling the function directly.

I've tested this locally this time. Even small MRs can be wrong 🤦! apologies for the churn.

Without this MR, we get framework failures in the testsuite and the testsuite lint pass (rightly) fails: https://gitlab.haskell.org/doyougnu/ghc/-/jobs/1262926

ping: @mpickering