tests: net_buf: buf: remove double free

`net_buf_frag_del` already unreferences the deleted fragment.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

tests/lib/net_buf/buf/prj.conf

@@ -1,5 +1,4 @@
 CONFIG_NET_BUF=y
-CONFIG_NET_TEST=y
 CONFIG_HEAP_MEM_POOL_SIZE=4096
 #CONFIG_NET_BUF_LOG=y
 #CONFIG_NET_BUF_LOG_LEVEL_DBG=y

tests/lib/net_buf/buf/src/main.c

@@ -288,7 +288,6 @@ ZTEST(net_buf_tests, test_net_buf_4)
 
 		if ((i % 2) && next) {
 			net_buf_frag_del(frag, next);
-			net_buf_unref(next);
 			removed++;
 		} else {
 			frag = next;
@@ -312,7 +311,6 @@ ZTEST(net_buf_tests, test_net_buf_4)
 		struct net_buf *frag2 = buf->frags;
 
 		net_buf_frag_del(buf, frag2);
-		net_buf_unref(frag2);
 		removed++;
 	}