Remove unnecessary hlint ignores (#6341)

In modern hlint, the spurious parse errors are gone now that it no
longer uses HSE, and it's also smart enough to avoid the bad "Use =="
suggestions itself.

.hlint.yaml

@@ -58,10 +58,8 @@
 - ignore: {name: "Eta reduce"}
 - ignore: {name: "Evaluate"}
 - ignore: {name: "Monad law, left identity", module: "Text.Pandoc.App.OutputSettings"}
-- ignore: {name: "Parse error"}  # we trust the compiler over HLint
 - ignore: {name: "Reduce duplication", module: "Text.Pandoc.Readers.Markdown"}
 - ignore: {name: "Use &&&"}
-- ignore: {name: "Use =="}  # Creates infinite loops in `EQ` using expressions
 - ignore: {name: "Use String"}
 - ignore: {name: "Use fmap"}  # specific for GHC 7.8 compat
 - ignore: {name: "Use forM_", module: "Text.Pandoc.Readers.DocBook"}