configure: add missing optional dep on libfribidi to the drawtext filter

Fixes ticket #6740
Signed-off-by: James Almer <jamrial@gmail.com>

configure

@@ -3224,7 +3224,7 @@ delogo_filter_deps="gpl"
 deshake_filter_select="pixelutils"
 deshake_filter_suggest="opencl"
 drawtext_filter_deps="libfreetype"
-drawtext_filter_suggest="libfontconfig"
+drawtext_filter_suggest="libfontconfig libfribidi"
 elbg_filter_deps="avcodec"
 eq_filter_deps="gpl"
 fftfilt_filter_deps="avcodec"