Remove spurious ACLOCAL_FLAGS variable from autogen.sh.

autoreconf looks for ACLOCAL_*FLAGS in Makefile.am and will
pass that on when it invokes aclocal. Furthermore, setting
a local like this doesn't make it available to subcommands,
so the line has no effect.

autogen.sh

@@ -7,5 +7,4 @@ test -n "$srcdir" && cd "$srcdir"
 
 echo "Updating build configuration files for opusfile, please wait...."
 
-ACLOCAL_FLAGS="-I m4"
 autoreconf -isf