[fix compile warning] remove useless local variable
[fix compile warning] remove useless local variable

compile log:
khttp.c:1483:19: warning: unused variable 'end' [-Wunused-variable]
            char *end = strstr(data, "\r\n\r\n");
                  ^
1 warning generated.

zlargon/khttp,kaija/khttp,zlargon/khttp,kaija/khttp,zlargon/khttp,zlargon/khttp