VS: Fix support for '/guard:cf' linker flag for v142

Apply the change from commit 57a78b5526 (VS: Fix support for '/guard:cf'
linker flag, 2018-11-21) to the v142 flag table.

Although `$(VCTargetsPath)/1033/link.xml` contains an entry for
`LinkControlFlowGuard`, it does not work when used in a `.vcxproj` file
(at least as of v140 and v141).  Drop our link flag table entries for
these toolsets so that the flag will be passed via `AdditionalOptions`.

Templates/MSBuild/FlagTables/v142_Link.json

@@ -546,13 +546,6 @@
     "value": "SystemDlls",
     "flags": []
   },
-  {
-    "name": "LinkControlFlowGuard",
-    "switch": "guard:cf",
-    "comment": "Enable Security Check with Guard",
-    "value": "Guard",
-    "flags": []
-  },
   {
     "name": "LinkIncremental",
     "switch": "INCREMENTAL:NO",