adjust redex error message tests to match singular/plural fixes in

the error raising code, except in one place where I think the
error raising code was correct to have the plural form, so I changed
it back instead of changing the Redex test suite to match

collects/racket/private/sc.rkt

@@ -567,7 +567,7 @@
                                        (apply
                                         raise-syntax-error 
                                         'syntax
-                                        "too many ellipsis in template"
+                                        "too many ellipses in template"
                                         (pick-specificity
                                          top
                                          last-el))))]

collects/redex/tests/rg-test.rkt

@@ -226,7 +226,7 @@
   (test (with-handlers ([exn:fail:syntax? exn-message])
           (parameterize ([current-namespace ns])
             (expand #'(generate-term M n))))
-        #rx"generate-term: expected an identifier defined by define-language( in: M)?$")
+        #rx"generate-term: expected an identifier defined by define-language([\n ]+in: M)?(\n|$)")
   (test-contract-violation/client (generate-term L n 1.5))
   (test-contract-violation/client (generate-term L n 1 #:retries .5))
   (test-contract-violation/client (generate-term L n 1 #:attempt-num .5))

collects/redex/tests/syn-err-tests/judgment-form-definition.rktd

@@ -157,7 +157,7 @@
      [(uses-unquote n unq)])
    (void)))
 
-(#rx"missing ellipses"
+(#rx"missing ellipsis"
  ([use any_0]) ([ellipsis ...] [def any_0])
  (let ()
    (define-judgment-form syn-err-lang

collects/redex/tests/syn-err-tests/term.rktd

@@ -1,4 +1,4 @@
-(#rx"missing ellipses"
+(#rx"missing ellipsis"
  ([id-no-ellipsis x]) ([ellipsis ...])
  (term-let ([(id-no-ellipsis ellipsis) '(a b c)]) (term id-no-ellipsis)))