doc: build: docker: Use code-block for syntax highlighting

Use ..code-block:: syntax highlighting instead of :: so all bash
commands use the same syntax highlighting.

Signed-off-by: Leonard Anderweit <l.anderweit@phytec.de>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
diff --git a/doc/build/docker.rst b/doc/build/docker.rst
index fe08765..4974a98 100644
--- a/doc/build/docker.rst
+++ b/doc/build/docker.rst
@@ -12,7 +12,9 @@
     ERROR: Multi-platform build is not supported for the docker driver.
     Switch to a different driver, or turn on the containerd image store, and try again.
 
-You can add a simple one with::
+You can add a simple one with:
+
+.. code-block:: bash
 
     sudo docker buildx create --name multiarch --driver docker-container --use
 
@@ -20,7 +22,9 @@
 architectures request in a build.  While both amd64 and arm64 happen in
 parallel, the non-native part will take considerably longer as it must use QEMU
 to emulate the foreign code.  An alternative, if you have accesss to reasonably
-fast amd64 (i.e. 64-bit x86) and arm64 machines is::
+fast amd64 (i.e. 64-bit x86) and arm64 machines is:
+
+.. code-block:: bash
 
     sudo docker buildx create --name multiarch-multinode --node localNode --bootstrap --use
     sudo docker buildx create --name multiarch-multinode --append --node remoteNode --bootstrap ssh://user@host