all: fix typos where we repeat repeat ourselves

Found with the regex `\b([A-Za-z]+) \1\b`.

Updates #cleanup

Change-Id: I4cc51784d9b6437d3d0c66b531828707f87f7fd5
Signed-off-by: Alex Chan <alexc@tailscale.com>

ipn/store/awsstore/store_aws.go

@@ -79,7 +79,7 @@ type awsStore struct {
 //
 // Note that we store the entire store in a single parameter
 // key, therefore if the state is above 8kb, it can cause
-// Tailscaled to only only store new state in-memory and
+// Tailscaled to only store new state in-memory and
 // restarting Tailscaled can fail until you delete your state
 // from the AWS Parameter Store.
 //