Remove unused aegisCache map

Operations having to do with issuing nuke punishments and undoing said
punishments rely on the `singleUserAegisCache` map and the
`nukedPhrases` array. It appears the `aegisCache` offers no utility, so
it can be removed.

lib/services/punishment-cache.js

@@ -19,7 +19,6 @@ class PunishmentCache {
      * @type {Object.<string, PunishedViewer>}
      */
     this.punishedViewersMap = {};
-    this.aegisCache = [];
     this.singleUserAegisCache = {};
     this.timeToLive = config.timeToLiveSeconds || 1800;
     this.tombStoneInterval = config.tomeStoneIntervalMilliseconds || 120000;
@@ -60,7 +59,6 @@ class PunishmentCache {
   }
 
   addNukeToCache(userList, nukedPhrase, duration, isMegaNuke) {
-    this.aegisCache.push({ nukedPhrase, userList });
     this.nukedPhrases.push({ duration, phrase: nukedPhrase, isMegaNuke });
     userList.forEach((user) => {
       this.addUserToAegisCache(user, duration, nukedPhrase);
@@ -82,14 +80,6 @@ class PunishmentCache {
         nukedPhrase.phrase instanceof RegExp ? nukedPhrase.phrase.toString() : nukedPhrase.phrase;
       return curPhrase.toLowerCase() !== nuke.toLowerCase();
     });
-
-    this.aegisCache = this.aegisCache.filter((nukedPhrase) => {
-      const curPhrase =
-        nukedPhrase.nukedPhrase instanceof RegExp
-          ? nukedPhrase.nukedPhrase.toString()
-          : nukedPhrase.nukedPhrase;
-      return curPhrase.toLowerCase() !== nuke.toLowerCase();
-    });
   }
 
   cleanseNukes() {