Fix the antispam test: pin the rules it scores against, stop live Pyzor

It failed everywhere but upstream's machines, for two reasons:

- The spam rules, which carry every score, came from a path on an
  upstream developer's own disk. Without SPAM_RULES_URL none loaded, every
  score was 0.00 and the combined case came out ham instead of spam at
  13.70. The published rules of spam-filter v3.0.2 are now pinned beside
  the test cases (Apache-2.0 or MIT, taken as MIT; in THIRD-PARTY.md).
  SPAM_RULES_URL still overrides.
- The first combined case expects a Pyzor hit, and its digest (that of an
  empty body) wasn't among the three the test mode answers, so it went to
  a public Pyzor server: it failed offline and would drift with that
  server's counts. Test mode now answers every digest from a fixed table,
  with the empty body's added, and never reaches the network.

The test passes online and offline, alone and with the rest of the SMTP
tests. queue_retry, unrelated, still fails when it runs after the others
in one process, though it passes alone every time.

tests/src/smtp/inbound/antispam.rs

@@ -81,9 +81,18 @@ async fn antispam() {
     admin
         .registry_create_object(SpamSettings {
             score_spam: Float::new(5.0),
+            // inbuxa: the rules carry the scores the expectations are written
+            // against, so they're pinned (spam-filter v3.0.2, beside the test
+            // cases) rather than read from a developer's own checkout, which
+            // left every score at zero. SPAM_RULES_URL still overrides.
             spam_filter_rules_url: std::env::var("SPAM_RULES_URL")
                 .unwrap_or_else(|_| {
-                    "file:///Users/me/code/spam-filter/spam-filter-rules.json.gz".to_string()
+                    concat!(
+                        "file://",
+                        env!("CARGO_MANIFEST_DIR"),
+                        "/resources/smtp/antispam/spam-filter-rules.json.gz"
+                    )
+                    .to_string()
                 })
                 .into(),
             ..Default::default()
@@ -156,7 +165,7 @@ async fn antispam() {
         }))
         .await;
     // inbuxa: a rules file that can't be read is retried later; don't wait
-    // for that retry (the path above is a developer's own checkout)
+    // for that retry (SPAM_RULES_URL may name one that isn't there)
     test.wait_for_tasks_skip_not_due().await;
     admin.reload_settings().await;
     admin.reload_lookup_stores().await;