- Add auto-generated _en.ts files to .gitignore.
- Let git do the globbing by passing the pattern on to git so that
  git add will not bail out with error when encountering
  a file listed in .gitignore.

Task-number: QTBUG-48075
Change-Id: I2ab328a9ef4574e15742af2dafecda52f795685a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>