Remove "deriving" Haskell artifact from indentation

`deriving` isn't a thing in PureScript. There's `derive` keyword, but
it has a bit different structure (specifically, it is a top-level
keyword).

Related discussion: https://discourse.purescript.org/t/solved-is-deriving-keyword-a-thing-in-purescript/4787

Author: Hi-Angel

purescript-indentation.el

@@ -649,7 +649,7 @@ indent the current line. This has to be fixed elsewhere."
      (purescript-indentation-type)
      (cond ((string= current-token "=")
             (purescript-indentation-with-starter
-             (lambda () (purescript-indentation-separated #'purescript-indentation-type "|" "deriving"))
+             (lambda () (purescript-indentation-separated #'purescript-indentation-type "|" nil))
              nil))
            ((string= current-token "where")
             (purescript-indentation-with-starter
@@ -998,7 +998,7 @@ indent the current line. This has to be fixed elsewhere."
 
 (defun purescript-indentation-peek-token ()
   "Return token starting at point."
-  (cond ((looking-at "\\(if\\|then\\|else\\|let\\|in\\|ado\\|mdo\\|rec\\|\\(?:[[:word:]]+\\.\\)*do\\|proc\\|case\\|of\\|where\\|module\\|deriving\\|data\\|type\\|newtype\\|class\\|instance\\)\\([^[:alnum:]'_]\\|$\\)")
+  (cond ((looking-at "\\(if\\|then\\|else\\|let\\|in\\|ado\\|mdo\\|rec\\|\\(?:[[:word:]]+\\.\\)*do\\|proc\\|case\\|of\\|where\\|module\\|data\\|type\\|newtype\\|class\\|instance\\)\\([^[:alnum:]'_]\\|$\\)")
          (match-string-no-properties 1))
         ((looking-at "[][(){}[,;]")
          (match-string-no-properties 0))