Upgrade to Panda v7 - support key rotation

This upgrades Panda from v5 to v7, allowing us to use key rotation as
introduced with guardian/pan-domain-authentication#150.

As Atom Workshop is pretty standard user of Panda, the upgrade is pretty simple:

* Panda v6:
  * guardian/pan-domain-authentication#155 requires
    `panDomainSettings` is a `val`, not a `def`

project/Dependencies.scala

@@ -33,7 +33,7 @@ object Dependencies {
     "com.gu" %% "editorial-permissions-client" % "2.15",
     "com.gu" %% "simple-configuration-ssm" % "1.5.6",
     "com.gu" %% "fezziwig" % "1.6",
-    "com.gu" %% "pan-domain-auth-play_3-0" % "6.0.0-PREVIEW.support-accepting-multiple-public-keys.2024-09-12T1504.6e11a68d",
+    "com.gu" %% "pan-domain-auth-play_3-0" % "7.0.0",
     "io.circe" %% "circe-parser" % "0.14.5",
     "net.logstash.logback" % "logstash-logback-encoder" % "6.6",
     "com.gu" %% "content-api-client-aws" % "0.7",