doc: bump version to 3.3.1

doc/fcft_capabilities.3.scd

doc/fcft_clone.3.scd

doc/fcft_destroy.3.scd

doc/fcft_fini.3.scd

doc/fcft_font_options_create.3.scd

doc/fcft_font_options_destroy.3.scd

doc/fcft_from_name.3.scd

doc/fcft_from_name2.3.scd

doc/fcft_init.3.scd

doc/fcft_kerning.3.scd

doc/fcft_log_init.3.scd

doc/fcft_precompose.3.scd

doc/fcft_rasterize_char_utf32.3.scd

doc/fcft_rasterize_grapheme_utf32.3.scd

doc/fcft_rasterize_text_run_utf32.3.scd

doc/fcft_set_emoji_presentation.3.scd

doc/fcft_set_scaling_filter.3.scd

doc/fcft_text_run_destroy.3.scd