Increase default width of launch configuration dialog

Summary:
The patch goal is fix launch configuration dialog UI for cases with long strings, like in russian locale.

The presented screenshots shows that old version provides too small dialog width, which leads to unreadable text in "Debugger" combobox.

Old version:

New version:

Test Plan: Tested on master branch

Reviewers: KDevelop, kfunk

Reviewed By: KDevelop, kfunk

Subscribers: kdevelop-devel

Differential Revision: https://phabricator.kde.org/D4615

(cherry picked from commit e2740688e0229127d5f4891b9297131467457907)