Remove more references to GAE (#2894)

These are old/pointless now that we've migrated to GKE. Note that this
doesn't update anything in the docs/ folder, as that's a much larger
project that should be done on its own.

common/src/main/java/google/registry/util/DateTimeUtils.java

@@ -33,8 +33,8 @@ public abstract class DateTimeUtils {
   /**
    * A date in the far future that we can treat as infinity.
    *
-   * <p>This value is (2^63-1)/1000 rounded down. AppEngine stores dates as 64 bit microseconds, but
-   * Java uses milliseconds, so this is the largest representable date that will survive a
+   * <p>This value is (2^63-1)/1000 rounded down. Postgres can store dates as 64 bit microseconds,
+   * but Java uses milliseconds, so this is the largest representable date that will survive a
    * round-trip through the database.
    */
   public static final DateTime END_OF_TIME = new DateTime(Long.MAX_VALUE / 1000, DateTimeZone.UTC);