Minor misc cleanups

- GHC.HsToCore.Foreign.JavaScript: remove dropRuntimeRepArgs;
  boxed tuples don't take RuntimeRep args
- GHC.HsToCore.Foreign.Call: avoid partial pattern matching
- GHC.Stg.Unarise: strengthen the assertion; we can assert that
  non-rubbish literals are unary rather than just non-void
- GHC.Tc.Gen.HsType: make sure the fsLit "literal" rule fires
- users_guide/using-warnings.rst: remove -Wforall-identifier,
  now deprecated and does nothing
- users_guide/using.rst: fix formatting
- andy_cherry/test.T: remove expect_broken_for(23272...), 23272 is fixed

The rest are simple cleanups.