[docs] Don't use the `asm` syntax highlighting (which our docs builder

errors on) and clean up the formattting.

This isn't actualy assembly anyways, so dropping the highlighting is
probably for the best.

llvm-svn: 338979

clang/docs/HardwareAssistedAddressSanitizerDesign.rst

@@ -47,7 +47,7 @@ All memory accesses are prefixed with an inline instruction sequence that
 verifies the tags. Currently, the following sequence is used:
 
 
-.. code-block:: asm
+.. code-block:: none
 
   // int foo(int *a) { return *a; }
   // clang -O2 --target=aarch64-linux -fsanitize=hwaddress -c load.c