docs: fixup broken markup

We need an empty line after ".. code-block: [...]", otherwise the first
lines are interpreted as arguments, not content. This makes the entire
code-blocks not render at all.

Fixes: 5d6d67a4d1 ("docs/android: improve documentation about building llvmpipe for Android")
Reviewed-by: Dylan Baker <None>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32831>

docs/drivers/llvmpipe.rst

@@ -98,6 +98,7 @@ You need to set the ``ANDROID_NDK_ROOT``, ``ANDROID_SDK_VERSION`` and
 ``LLVML_INSTALL_PREFIX`` environment variables appropriately.
 
 .. code-block:: sh
+
    #!/bin/bash
 
    set -e
@@ -146,6 +147,7 @@ The list of libraries passed in `dep_llvm` below should match what it was
 produced by the LLVM build from above.
 
 .. code-block:: sh
+
    #!/usr/bin/env bash
 
    set -exu