internal/trace: rename trivialEnder to trivialSpan

Since we renamed the Ender interface to Span in the review of CL
523739.

For golang/go#61399

Change-Id: I8bcc47a709f5d154d61c2a886270c5fea4cf22b3
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/524495
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
kokoro-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/internal/trace/trace.go b/internal/trace/trace.go
index 44567ae..8517aab 100644
--- a/internal/trace/trace.go
+++ b/internal/trace/trace.go
@@ -13,10 +13,6 @@
 	End()
 }
 
-type trivialEnder struct{}
-
-func (trivialEnder) End() {}
-
 var startSpan func(context.Context, string) (context.Context, Span)
 
 // SetTraceFunction sets StartSpan to call the given function to start
@@ -31,5 +27,9 @@
 	if startSpan != nil {
 		return startSpan(ctx, name)
 	}
-	return ctx, trivialEnder{}
+	return ctx, trivialSpan{}
 }
+
+type trivialSpan struct{}
+
+func (trivialSpan) End() {}