Fix definesandincludes test.

Summary:
The code as it currently stands do not return any parser arguments for any `LanguageType::Other` files.
The checks I removed were added for this commit: https://phabricator.kde.org/R32:1c78a564626a0e5e305383c5fdb36b0fc76073cc
However, I can't find it in the history:  https://phabricator.kde.org/source/kdevelop/history/master/plugins/custom-definesandincludes/definesandincludesmanager.cpp
I suspect it wasn't merged properly and got lost.

Anyway, now `parserArguments` tries to guess language type for a file requested and for `ProjectFolderItem` `LanguageType::Other` is returned.

Reviewers: #kdevelop, skalinichev

Subscribers: kdevelop-devel

Tags: #kdevelop

Differential Revision: https://phabricator.kde.org/D13537