Docs: Fix some document build warnings

Fix some duplicated labels warnings and code block language warnings.

Change-Id: Ic25be83273fb8eac3a3ff4c2b98182ff268cb3dd
Signed-off-by: David Hu <david.hu@arm.com>
diff --git a/docs/technical_references/tfm_secure_irq_handling.rst b/docs/technical_references/tfm_secure_irq_handling.rst
index 8cd664e..469d044 100644
--- a/docs/technical_references/tfm_secure_irq_handling.rst
+++ b/docs/technical_references/tfm_secure_irq_handling.rst
@@ -153,7 +153,7 @@
 interrupt of 'A' is triggered, and then this last handler is interrupted. At
 this point the context stack looks like this:
 
-.. code-block::
+.. code-block:: rst
 
   +------------+
   | [intr_ctx] |
@@ -172,11 +172,10 @@
 
 So the max stack size can be calculated as a function of the IRQ count of 'A':
 
-.. code-block::
-
+.. code-block:: c
 
   max_stack_size = intr_ctx_size + (IRQ_CNT * (intr_ctx_size + hndl_ctx_size))
 
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+*Copyright (c) 2018-2021, Arm Limited. All rights reserved.*