doc: Fix code blocks in thread_local_storage.rst

Add missing blank line before the code block to
render it correctly.

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

Documentation/guides/thread_local_storage.rst

@@ -28,6 +28,7 @@ If your compiler support it then you still need further configuration to use it:
 2. Handle ``tbss`` and ``tdata`` sections in linker script, your can refer to the example in rv-virt
 
 To confirm that your compiler supports TLS, you can try this command:
+
 .. code-block:: console
 
     arm-none-eabi-gcc --verbose