dashboard/app: reduce auto-closing timeout to 120 days

See #1054

First simple step.
diff --git a/dashboard/app/notifications_test.go b/dashboard/app/notifications_test.go
index 093c6a7..bbd5d7c 100644
--- a/dashboard/app/notifications_test.go
+++ b/dashboard/app/notifications_test.go
@@ -124,7 +124,7 @@
 	c.expectNoEmail()
 
 	// Not yet.
-	c.advanceTime(179 * 24 * time.Hour)
+	c.advanceTime(119 * 24 * time.Hour)
 	c.expectNoEmail()
 
 	// Now!
@@ -145,7 +145,7 @@
 	c.incomingEmail(report.Sender, "#syz upstream")
 	report = c.pollEmailBug()
 
-	c.advanceTime(181 * 24 * time.Hour)
+	c.advanceTime(121 * 24 * time.Hour)
 	notif = c.pollEmailBug()
 	if !strings.Contains(notif.Body, "Auto-closing this bug as obsolete") {
 		t.Fatalf("bad notification text: %q", notif.Body)
@@ -190,7 +190,7 @@
 	c.incomingEmail(report4.Sender, "#syz upstream")
 	report4 = c.pollEmailBug()
 
-	c.advanceTime(179 * 24 * time.Hour)
+	c.advanceTime(119 * 24 * time.Hour)
 	c.expectNoEmail()
 
 	c.client2.ReportCrash(crash2)
diff --git a/dashboard/app/reporting.go b/dashboard/app/reporting.go
index 417f3a9..99adb19 100644
--- a/dashboard/app/reporting.go
+++ b/dashboard/app/reporting.go
@@ -31,7 +31,7 @@
 	maxInlineError             = 16 << 10
 	notifyResendPeriod         = 14 * 24 * time.Hour
 	notifyAboutBadCommitPeriod = 90 * 24 * time.Hour
-	autoObsoletePeriod         = 180 * 24 * time.Hour
+	autoObsoletePeriod         = 120 * 24 * time.Hour
 	internalError              = "internal error"
 	// This is embedded as first line of syzkaller reproducer files.
 	syzReproPrefix = "# See https://goo.gl/kgGztJ for information about syzkaller reproducers.\n"