[docs][GlobalISel] Fix the warnings during docs-llvm-html build

Before the fix the build of docs-llvm-html would fail.
The rG8bc03d216824 introduced a reference to an undefined label,
so we have warning as:

  llvm-project/llvm/docs/GlobalISel/GenericOpcode.rst:295:\
  undefined label: i_intr_llvm_ptrmask (if the link has no\
  caption the label must precede a section header)

diff --git a/llvm/docs/GlobalISel/GenericOpcode.rst b/llvm/docs/GlobalISel/GenericOpcode.rst
index 33611ea..5c0be7e 100644 (file)
--- a/llvm/docs/GlobalISel/GenericOpcode.rst
+++ b/llvm/docs/GlobalISel/GenericOpcode.rst
@@ -294,7 +294,7 @@ G_PTRMASK
 
 Zero out an arbitrary mask of bits of a pointer. The mask type must be
 an integer, and the number of vector elements must match for all
-operands. This corresponds to :ref:`i_intr_llvm_ptrmask`.
+operands. This corresponds to `i_intr_llvm_ptrmask`.
 
 .. code-block:: none