Use an example address in the participants fixture

One test built its organizer from a real, routable address and a real
name. Every other fixture in the codebase uses example.org or
example.com, and this repository is public, so the odd one out was a
personal address sitting in public source for no reason -- the test
asserts roles and participation status and never looks at either value.

Now [email protected], matching what the rest of the tests already use.

Found while checking, at the maintainer's prompting, whether the repo
leaked anything about the host it runs on. It does not: the nginx and
deploy files here are the generic examples they claim to be, and the real
ones live in a private repository. This was the only thing the search
turned up that was worth changing.

web/src/store/__tests__/participants.test.ts

@@ -41,7 +41,7 @@ describe("makeParticipant", () => {
     expect(guest.expectReply).toBe(true);
   });
   it("marks the organizer as owner and keeps a status already given", () => {
-    const me = makeParticipant("john@linuxexperts.net", "John Coffey", "owner");
+    const me = makeParticipant("john@example.org", "John Doe", "owner");
     expect(me.roles).toEqual({ owner: true, attendee: true });
     expect(me.participationStatus).toBe("accepted");
     expect(me.expectReply).toBe(false);