set shm_size back to avoid a chrome crash (bus error)

Example crash log:

(google-chrome:13): LIBDBUSMENU-GLIB-WARNING **: Unable to get session bus: Failed to execute child process ?dbus-launch? (No such file or directory)
Bus error (core dumped)

docker-compose.yml

@@ -34,7 +34,7 @@ services:
       - IPC_LOCK # lock memory to prevent sensitive values from being swapped to disk.
     # Turns off anonymous page swapping
     mem_swappiness: 0
-    # shm_size: 4G
+    shm_size: 4G
     # mem_limit: 4G
     # security_opt:
       # - apparmor:docker-ptrace