Integers are primitive types. Update the documentation to state this

This was done for label, void, floating point, x86mmx, metadata,
just not integer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122606 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.html

@@ -1496,6 +1496,7 @@ <h5>Syntax:</h5>
       <td><a href="#t_primitive">primitive</a></td>
       <td><a href="#t_label">label</a>,
           <a href="#t_void">void</a>,
+          <a href="#t_integer">integer</a>,
           <a href="#t_floating">floating point</a>,
           <a href="#t_x86mmx">x86mmx</a>,
           <a href="#t_metadata">metadata</a>.</td>