testament spec: remove errmsg alias of errormsg (#16188)

testament/specs.nim

@@ -306,7 +306,7 @@ proc parseSpec*(filename: string): TSpec =
         result.msg = e.value
         if result.action != actionRun:
           result.action = actionCompile
-      of "errormsg", "errmsg": # xxx just use errormsg, no need for such aliases
+      of "errormsg":
         result.msg = e.value
         result.action = actionReject
       of "nimout":

testament/tests/shouldfail/tfile.nim

@@ -1,5 +1,5 @@
 discard """
-errmsg: "undeclared identifier: 'undefined'"
+errormsg: "undeclared identifier: 'undefined'"
 file: "notthisfile.nim"
 """