Fix JavaTimeDefaultTimeZone error flagged by error prone

Running recent error prone version complaining on that code:

TimeMachine.java:54: error: [JavaTimeDefaultTimeZone] Clock.systemDefaultZone()
is not allowed because it silently uses the system default time-zone.
You must pass an explicit time-zone (e.g., ZoneId.of("America/Los_Angeles")
 to this method.
    clock = Clock.systemDefaultZone();
                                   ^
    (see https://errorprone.info/bugpattern/JavaTimeDefaultTimeZone)

Bug: Issue 12677
Change-Id: I10e34bf90d1903aeb40810509b87b0519971ade1
diff --git a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/TimeMachine.java b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/TimeMachine.java
index c4fe5c0..53241ac 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/TimeMachine.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/TimeMachine.java
@@ -26,7 +26,8 @@
  */
 public class TimeMachine {
 
-  private static Clock clock = Clock.systemDefaultZone();
+  private static ZoneId PACIFIC_TIME_ZONE = ZoneId.of("America/Los_Angeles");
+  private static Clock clock = Clock.system(PACIFIC_TIME_ZONE);
 
   /**
    * Obtain the current instant on the time-line from the system clock using the system default time
@@ -45,12 +46,12 @@
    */
   @VisibleForTesting
   public static void useFixedClockAt(Instant instant) {
-    clock = Clock.fixed(instant, ZoneId.systemDefault());
+    clock = Clock.fixed(instant, PACIFIC_TIME_ZONE);
   }
 
-  /** Reset the clock to be the system default. */
+  /** Reset the clock to be the system PCT. */
   @VisibleForTesting
-  public static void useSystemDefaultZoneClock() {
-    clock = Clock.systemDefaultZone();
+  public static void useSystemPctZoneClock() {
+    clock = Clock.system(PACIFIC_TIME_ZONE);
   }
 }
diff --git a/src/test/java/com/googlesource/gerrit/plugins/deleteproject/fs/ArchiveRepositoryRemoverTest.java b/src/test/java/com/googlesource/gerrit/plugins/deleteproject/fs/ArchiveRepositoryRemoverTest.java
index 64634b9..e94390c 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/deleteproject/fs/ArchiveRepositoryRemoverTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/deleteproject/fs/ArchiveRepositoryRemoverTest.java
@@ -101,7 +101,7 @@
                   PLUGIN_NAME, archiveRepo));
       assertDirectoryContents(archiveRepo, true);
     } finally {
-      TimeMachine.useSystemDefaultZoneClock();
+      TimeMachine.useSystemPctZoneClock();
     }
   }