docs: Propagate fix from r165632 to other docs.

There are only two other instances of using `.. code::` instead of
`..  code-block::`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165633 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ExtendingLLVM.rst b/docs/ExtendingLLVM.rst
index e41cfd9..6df08ee 100644
--- a/docs/ExtendingLLVM.rst
+++ b/docs/ExtendingLLVM.rst
@@ -270,7 +270,7 @@
 
    add support for derived type to:
 
-   .. code:: c++
+   .. code-block:: c++
 
      std::string getTypeDescription(const Type &Ty,
                                     std::vector<const Type*> &TypeStack)
@@ -296,7 +296,7 @@
 
    modify
 
-   .. code:: c++
+   .. code-block:: c++
 
      void calcTypeName(const Type *Ty,
                        std::vector<const Type*> &TypeStack,