configure: remove typo for zlib

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/configure b/configure
index 9c64d14..5fd0c50 100755
--- a/configure
+++ b/configure
@@ -420,7 +420,7 @@
 # zlib probe
 zlib="no"
 cat > $TMPC <<EOF
-#include <zlib2.h>
+#include <zlib.h>
 int main(void)
 {
   z_stream stream;