trying to fix build error

docs/getting-started-guides/docker.md

@@ -59,12 +59,11 @@ Here's a diagram of what the final result will look like:
 following configs are turned on in your linux kernel:
 
     ```console
-
-    CONFIG_RESOURCE_COUNTERS=y 
-    CONFIG_MEMCG=y 
-    CONFIG_MEMCG_SWAP=y 
-    CONFIG_MEMCG_SWAP_ENABLED=y 
-    CONFIG_MEMCG_KMEM=y 
+    CONFIG_RESOURCE_COUNTERS=y
+    CONFIG_MEMCG=y
+    CONFIG_MEMCG_SWAP=y
+    CONFIG_MEMCG_SWAP_ENABLED=y
+    CONFIG_MEMCG_KMEM=y
     ```
 
 3. Enable the memory and swap accounting in the kernel, at boot, as command line
@@ -74,12 +73,12 @@ parameters as follows:
     GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"
     ```
 
-    NOTE: The above is specifically for GRUB2. 
+    NOTE: The above is specifically for GRUB2.
     You can check the command line parameters passed to your kenel by looking at the
     output of /proc/cmdline:
 
     ```console
-    $cat /proc/cmdline 
+    $cat /proc/cmdline
     BOOT_IMAGE=/boot/vmlinuz-3.18.4-aufs root=/dev/sda5 ro cgroup_enable=memory
     swapaccount=1
     ```