Summary:
When `(.) @Int` is used without enabling `TypeApplications`,
the resulting error message will pretty-print the (symbolic)
`RdrName` `(.)`. However, it does so without parenthesizing it, which
causes the pretty-printed expression to appear as `.@Int`. Yuck.

Since the expression in a type application will always be prefix,
we can fix this issue by using `pprPrefixOcc` instead of plain ol'
`ppr`.

Test Plan: make test TEST=T15527

Reviewers: bgamari, monoidal, simonpj

Reviewed By: monoidal, simonpj

Subscribers: rwbarton, carter

GHC Trac Issues: #15527

Differential Revision: https://phabricator.haskell.org/D5071

(cherry picked from commit 5238f204)