fix(test): pass the now-required sessionGrants in RelayAuthReadFollowsTest

A semantic merge conflict: no textual overlap, but the two sides do not compile
together.

Making RelayAuthPermissionLedger.sessionGrants required (no default) updated
every ledger construction its author could see. RelayAuthReadFollowsTest was
not one of them — it arrived independently from main, so neither branch was
broken on its own and git had nothing to flag. Merging them produced
"No value passed for parameter 'sessionGrants'".

Passes a fresh RelayAuthSessionGrants() like the sibling suites. A private set
is right here: this test never exercises grants, it only needs a ledger.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rado2dnqpbCuCUyCd3trQz

amethyst/src/test/java/com/vitorpamplona/amethyst/service/relayClient/authCommand/model/RelayAuthReadFollowsTest.kt

@@ -62,6 +62,7 @@ class RelayAuthReadFollowsTest {
         RelayAuthPermissionLedger(
             store = NoStore(),
             globalPolicy = { RelayAuthPolicy.CUSTOM },
+            sessionGrants = RelayAuthSessionGrants(),
             customToggles = { toggles },
             isFollowed = { it == followed },
         )