Remove timestamps so portage stops stating "your sync is X years old".

BUG=None
TEST=cros_sdk --replace

Change-Id: I2704d22f1c43b71e60b5315cb03fa95889b8d9e5
diff --git a/metadata/timestamp b/metadata/timestamp
deleted file mode 100644
index 9d28993..0000000
--- a/metadata/timestamp
+++ /dev/null
@@ -1 +0,0 @@
-Wed Mar 10 06:39:40 UTC 2010
diff --git a/metadata/timestamp.chk b/metadata/timestamp.chk
deleted file mode 100644
index 2261613..0000000
--- a/metadata/timestamp.chk
+++ /dev/null
@@ -1 +0,0 @@
-Wed, 10 Mar 2010 07:00:01 +0000
diff --git a/metadata/timestamp.x b/metadata/timestamp.x
deleted file mode 100644
index fd0cc63..0000000
--- a/metadata/timestamp.x
+++ /dev/null
@@ -1 +0,0 @@
-1268202901 Wed Mar 10 06:35:01 2010 UTC