Remove superfluous include from filter-avcodec.pro

The config file filters/filter-avcodec.pro contains an invocation of include(../settings.pro), duplicating the same line in filter-common.pro . All build flags end up being duplicated because of this. For most flags that is meaningless but the stack-alignment flag is not so friendly at least on OSX.

Fixes #11149

Signed-off-by: Stuart Morgan <smorgan@mythtv.org>