Revert "[Docs][Windows Itanium] Add a How-To document for Windows Itanium."

This reverts commit 5a91d23.

Markup was incorrect.

Author: bd1976bris

llvm/docs/HowToBuildWindowsItaniumPrograms.rst

@@ -33,7 +33,6 @@ intermediate LLVM representation.
    GoldPlugin
    HowToBuildOnARM
    HowToBuildWithPGO
-   HowToBuildWindowsItaniumPrograms
    HowToCrossCompileBuiltinsOnArm
    HowToCrossCompileLLVM
    HowToUpdateDebugInfo
@@ -199,9 +198,6 @@ Additional Topics
    Gives the steps necessary when adding a new constrained math intrinsic
    to LLVM.
 
-:doc:`HowToBuildWindowsItaniumPrograms`
-   Notes on assembling a Windows Itanium enviroment.
-
 :doc:`HowToCrossCompileBuiltinsOnArm`
    Notes on cross-building and testing the compiler-rt builtins for Arm.