Set consistent column widths on Special:Version

After 9d616a7cc8adfff19af7479984e9909f0a7a43b0, it really bugs me that
the individual tables under "Installed extensions" all have different
columns widths. But even before that, the widths were weird (there are
some extensions with really long names or license codes that mess up
the tables). Set better defaults for them.

Bug: T363767
Change-Id: Idbf8512aa101c700908364c03cf8521dd99a7321