Respect updated path format when cleaning cache

Since d8114e8 the file name is used for caching as-is without adding
.jpg at the end, but sxiv -c still expected old format causing it to
remove all fresh thumbnails.

thumbs.c

@@ -120,8 +120,7 @@ void tns_cache_write(Imlib_Image im, const char *filepath, bool force)
 void tns_clean_cache(tns_t *tns)
 {
 	int dirlen;
-	bool delete;
-	char *cfile, *filename, *tpos;
+	char *cfile, *filename;
 	r_dir_t dir;
 
 	if (r_opendir(&dir, cache_dir, true) < 0) {
@@ -133,15 +132,7 @@ void tns_clean_cache(tns_t *tns)
 
 	while ((cfile = r_readdir(&dir, false)) != NULL) {
 		filename = cfile + dirlen;
-		delete = false;
-
-		if ((tpos = strrchr(filename, '.')) != NULL) {
-			*tpos = '\0';
-			if (access(filename, F_OK) < 0)
-				delete = true;
-			*tpos = '.';
-		}
-		if (delete) {
+		if (access(filename, F_OK) < 0) {
 			if (unlink(cfile) < 0)
 				error(0, errno, "%s", cfile);
 		}