Remove extra paragraph from license text.

Remove the "If only executable code is distributed..." paragraph from
the license text. Everything now uses a normal MIT license.

The only code from Khronos that's included in libglvnd is the EGL/GL
header and XML files, which do not contain that paragraph.

Fixes glvnd/libglvnd#221
12 jobs for fix-license-text in 3 minutes and 2 seconds (queued for 4 seconds)