remove deprecated specs (#16684)

testament/specs.nim

@@ -303,10 +303,6 @@ proc parseSpec*(filename: string): TSpec =
       of "exitcode":
         discard parseInt(e.value, result.exitCode)
         result.action = actionRun
-      of "msg":
-        result.msg = e.value
-        if result.action != actionRun:
-          result.action = actionCompile
       of "errormsg":
         result.msg = e.value
         result.action = actionReject

testament/tests/shouldfail/tmsg.nim

@@ -1,6 +0,0 @@
-discard """
-msg: "Hello World"
-"""
-
-static:
-  echo "something else"