package/gstreamer1/gst1-plugins-bad: bump version to 1.18.1

package/gstreamer1/gst1-plugins-bad: bump version to 1.18.1

Update license info:

- GPL-2.0+ text in COPYING was replaces with LGPL-2.0+ with
  commit [1]
- COPYING.LIB was removed and LGPL-2.0 replaced with LGPL-2.1+
  with commit [2]
- keep the license info to LGPL-2.0+ (as the source files state
  ('version 2 of the License, or (at your option) any later version')

[1] https://cgit.freedesktop.org/gstreamer/gst-plugins-bad/commit/?id=daf8f65be1cccbe0b22c0734732816af4911dcb5
[2] https://cgit.freedesktop.org/gstreamer/gst-plugins-bad/commit/?id=142c1e7a06301a92688830dcf04c04d21285a7e7

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>