docs: fix syntax highlighting on shell commands

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27010>

docs/submittingpatches.rst

@@ -174,7 +174,7 @@ to test this is to make use of the \`git rebase\` command, to run your
 tests on each commit. Assuming your branch is based off
 ``origin/main``, you can run:
 
-.. code-block:: console
+.. code-block:: sh
 
    $ git rebase --interactive --exec "meson test -C build/" origin/main
 
@@ -433,7 +433,7 @@ Git tips
 -  ``git rebase -i ...`` is your friend. Don't be afraid to use it.
 -  Apply a fixup to commit FOO.
 
-   .. code-block:: console
+   .. code-block:: sh
 
       git add ...
       git commit --fixup=FOO
@@ -441,6 +441,6 @@ Git tips
 
 -  Test for build breakage between patches e.g last 8 commits.
 
-   .. code-block:: console
+   .. code-block:: sh
 
       git rebase -i --exec="ninja -C build/" HEAD~8