run_as_ipc_client: free response after running the IPC command

Fixes memory leaks in the form of:

Direct leak of 24 byte(s) in 1 object(s) allocated from:
    #0 0x7f5f7c2f4f30 in __interceptor_malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0xedf30)
    swaywm#1 0x563c799569f2 in ipc_recv_response ../common/ipc-client.c:94
    swaywm#2 0x563c79957062 in ipc_single_command ../common/ipc-client.c:138
    swaywm#3 0x563c798a56cc in run_as_ipc_client ../sway/main.c:127
    swaywm#4 0x563c798a6a3a in main ../sway/main.c:349
    swaywm#5 0x7f5f7b4d609a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2409a)

sway/main.c

@@ -126,6 +126,7 @@ void run_as_ipc_client(char *command, char *socket_path) {
 	uint32_t len = strlen(command);
 	char *resp = ipc_single_command(socketfd, IPC_COMMAND, command, &len);
 	printf("%s\n", resp);
+	free(resp);
 	close(socketfd);
 }