Removed LGPL license text from CustomThreadFactory

CustomThreadFactory had *two* licenses in it: Apache 2.0 at the top, and LGPL next. It was the only file in BoneCP that has this text, so I assume it's there in error. Most likely this bit of LGPL text was missed when the project was moved over to the Apache license.

(This is an important change because the existence of that LGPL text blocks me from using BoneCP in my project.)