Sync parserTests with core.

This matches upstream core commit fb22c45886c6b63062dd45101a208294888e7ba9.

Jackmcbarn's patch https://gerrit.wikimedia.org/r/136234 to "Support
{{!}} as a magic word" seems to cause the tests "Parsoid: Merge double
tds (bug 50603)" and "Parsoid: Merge double tds in nested transclusion
content (bug 50603)" to fail, since Template:! is no longer defined in
parserTests.txt.

This is not an issue outside parserTests since Template:{{!}} continues 
to exist on the wikis where it is used.

Change-Id: I9a92b70edc959e3f223de51ca7b3e215797f7318