[docs] change a few code-blocks to llvm from text

llvm-svn: 309117
diff --git a/llvm/docs/GetElementPtr.rst b/llvm/docs/GetElementPtr.rst
index b593871..c2da640 100644
--- a/llvm/docs/GetElementPtr.rst
+++ b/llvm/docs/GetElementPtr.rst
@@ -196,7 +196,7 @@
 In order to access the 18th integer in the array, you would need to do the
 following:
 
-.. code-block:: text
+.. code-block:: llvm
 
   %idx = getelementptr { [40 x i32]* }, { [40 x i32]* }* %, i64 0, i32 0
   %arr = load [40 x i32]** %idx