[TargetRegistry] Remove deprecated createTargetMachine

This was included in the v21 release, so we can reasonably remove it
now. Add a TODO for the other functions that have not yet made it into a
release. It does not cost much to keep them around until the next
release given the small amount of code and should give a little bit of
extra time for some downstreams to migrate.

Author: boomanaiden154

llvm/include/llvm/MC/TargetRegistry.h

@@ -389,6 +389,7 @@ class Target {
   /// @name Feature Constructors
   /// @{
 
+  // TODO(boomanaiden154): Remove this function after LLVM 22 branches.
   [[deprecated("Use overload accepting Triple instead")]]
   MCAsmInfo *createMCAsmInfo(const MCRegisterInfo &MRI, StringRef TheTriple,
                              const MCTargetOptions &Options) const {
@@ -440,6 +441,7 @@ class Target {
     return MCInstrAnalysisCtorFn(Info);
   }
 
+  // TODO(boomanaiden154): Remove this function after LLVM 22 branches.
   [[deprecated("Use overload accepting Triple instead")]]
   MCRegisterInfo *createMCRegInfo(StringRef TT) const {
     if (!MCRegInfoCtorFn)
@@ -454,6 +456,7 @@ class Target {
     return MCRegInfoCtorFn(TT);
   }
 
+  // TODO(boomanaiden154): Remove this function after LLVM 22 branches.
   [[deprecated("Use overload accepting Triple instead")]]
   MCSubtargetInfo *createMCSubtargetInfo(StringRef TheTriple, StringRef CPU,
                                          StringRef Features) const {
@@ -496,16 +499,6 @@ class Target {
                                JIT);
   }
 
-  [[deprecated("Use overload accepting Triple instead")]]
-  TargetMachine *createTargetMachine(
-      StringRef TT, StringRef CPU, StringRef Features,
-      const TargetOptions &Options, std::optional<Reloc::Model> RM,
-      std::optional<CodeModel::Model> CM = std::nullopt,
-      CodeGenOptLevel OL = CodeGenOptLevel::Default, bool JIT = false) const {
-    return createTargetMachine(Triple(TT), CPU, Features, Options, RM, CM, OL,
-                               JIT);
-  }
-
   /// createMCAsmBackend - Create a target specific assembly parser.
   MCAsmBackend *createMCAsmBackend(const MCSubtargetInfo &STI,
                                    const MCRegisterInfo &MRI,
@@ -599,6 +592,7 @@ class Target {
     return nullptr;
   }
 
+  // TODO(boomanaiden154): Remove this function after LLVM 22 branches.
   [[deprecated("Use overload accepting Triple instead")]]
   MCRelocationInfo *createMCRelocationInfo(StringRef TT, MCContext &Ctx) const {
     return createMCRelocationInfo(Triple(TT), Ctx);
@@ -616,6 +610,7 @@ class Target {
     return Fn(TT, Ctx);
   }
 
+  // TODO(boomanaiden154): Remove this function after LLVM 22 branches.
   [[deprecated("Use overload accepting Triple instead")]]
   MCSymbolizer *
   createMCSymbolizer(StringRef TT, LLVMOpInfoCallback GetOpInfo,