Parser: remove unused rule (copy/paste error)

Summary:
Found out when tracking down conflicts reported by happy.
It was accidentally introduced in large Api Annotations
patch: 803fc5db31f084b73713342cdceaed5a9c664267

Before:
  unused rules: 1
  shift/reduce conflicts:  60
  reduce/reduce conflicts: 16
After:
  shift/reduce conflicts:  60
  reduce/reduce conflicts: 12

Unused rule is seen in happy's --info= output as:
    rule 180 is unused
    ...
    decl_cls -> 'default' infixexp '::' sigtypedoc     (180)
    decl_cls -> 'default' infixexp '::' sigtypedoc     (181)

While at it removed 'q' typo in parser conflict log :)

Signed-off-by: Sergei Trofimovich <siarheit@google.com>

Reviewers: simonmar, austin, alanz

Reviewed By: alanz

Subscribers: carter, thomie

Differential Revision: https://phabricator.haskell.org/D569