configure: Add fft dependency for showspatial filter.

Mentioned in ticket #8378.

configure

@@ -3548,6 +3548,7 @@ showcqt_filter_suggest="libfontconfig libfreetype"
 showcqt_filter_select="fft"
 showfreqs_filter_deps="avcodec"
 showfreqs_filter_select="fft"
+showspatial_filter_select="fft"
 showspectrum_filter_deps="avcodec"
 showspectrum_filter_select="fft"
 showspectrumpic_filter_deps="avcodec"