doc/developer: drop an outdated item

It dates back to pre-2005 days, when people generally tended to commit
their work directly without going through the mailing list. Few
developers do it today, and never outside of their standalone modules.
This item is thus confusing and misleading and is better removed.

doc/developer.texi

@@ -365,15 +365,6 @@ later on.
 Also if you have doubts about splitting or not splitting, do not hesitate to
 ask/discuss it on the developer mailing list.
 
-@subheading Ask before you change the build system (configure, etc).
-Do not commit changes to the build system (Makefiles, configure script)
-which change behavior, defaults etc, without asking first. The same
-applies to compiler warning fixes, trivial looking fixes and to code
-maintained by other developers. We usually have a reason for doing things
-the way we do. Send your changes as patches to the ffmpeg-devel mailing
-list, and if the code maintainers say OK, you may commit. This does not
-apply to files you wrote and/or maintain.
-
 @subheading Cosmetic changes should be kept in separate patches.
 We refuse source indentation and other cosmetic changes if they are mixed
 with functional changes, such commits will be rejected and removed. Every