player/command: add more precision to av speed correction pretty print

Those values are often very small, but it's still good information to
have how they are changing.

This brings those values closes to old `%+.05f%%` that were used here.

Author: kasper93

player/command.c

@@ -487,7 +487,7 @@ static int mp_property_av_speed_correction(void *ctx, struct m_property *prop,
     }
 
     if (action == M_PROPERTY_PRINT || action == M_PROPERTY_FIXED_LEN_PRINT) {
-        *(char **)arg = mp_format_double(NULL, (val - 1) * 100, 2, true,
+        *(char **)arg = mp_format_double(NULL, (val - 1) * 100, 4, true,
                                          true, action != M_PROPERTY_FIXED_LEN_PRINT);
         return M_PROPERTY_OK;
     }