util/hash-string: fix compile warning

util/hash-string: fix compile warning

Clang 19:

util-hash-string.c:41:16: error: implicit conversion loses integer precision: 'unsigned long' to 'int' [-Werror,-Wshorten-64-to-32]
   41 |     int len1 = strlen((char *)data1);
      |         ~~~~   ^~~~~~~~~~~~~~~~~~~~~
util-hash-string.c:42:16: error: implicit conversion loses integer precision: 'unsigned long' to 'int' [-Werror,-Wshorten-64-to-32]
   42 |     int len2 = strlen((char *)data2);
      |         ~~~~   ^~~~~~~~~~~~~~~~~~~~~
2 errors generated.