Get rid of str_contains()

We can use strchr() here.

src/common.c

@@ -163,18 +163,6 @@ str_replace(const char* string, const char* substr,
     return newstr;
 }
 
-int
-str_contains(const char str[], int size, char ch)
-{
-    int i;
-    for (i = 0; i < size; i++) {
-        if (str[i] == ch)
-            return 1;
-    }
-
-    return 0;
-}
-
 gboolean
 strtoi_range(char* str, int* saveptr, int min, int max, char** err_msg)
 {