Don't report signal: killed errors in serviceRPC (#18850)

Fix #18849

Signed-off-by: Andrew Thornton <art27@cantab.net>

routers/web/repo/http.go

@@ -495,7 +495,9 @@ func serviceRPC(ctx gocontext.Context, h serviceHandler, service string) {
 		Stdin:   reqBody,
 		Stderr:  &stderr,
 	}); err != nil {
+		if err.Error() != "signal: killed" {
 			log.Error("Fail to serve RPC(%s) in %s: %v - %s", service, h.dir, err, stderr.String())
+		}
 		return
 	}
 }