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>

derp/README.md

@@ -39,7 +39,7 @@ geographic regions to make sure users have low latency to their DERP home.
 Regions generally have multiple nodes per region "meshed" (routing to each
 other) together for redundancy: it allows for cloud failures or upgrades without
 kicking users out to a higher latency region. Instead, clients will reconnect to
-the next node in the region. Each node in the region is required to to be meshed
+the next node in the region. Each node in the region is required to be meshed
 with every other node in the region and forward packets to the other nodes in
 the region. Packets are forwarded only one hop within the region. There is no
 routing between regions. The assumption is that the mesh TCP connections are

derp/derp_client.go

@@ -69,7 +69,7 @@ type clientOpt struct {
 func MeshKey(k key.DERPMesh) ClientOpt { return clientOptFunc(func(o *clientOpt) { o.MeshKey = k }) }
 
 // IsProber returns a ClientOpt to pass to the DERP server during connect to
-// declare that this client is a a prober.
+// declare that this client is a prober.
 func IsProber(v bool) ClientOpt { return clientOptFunc(func(o *clientOpt) { o.IsProber = v }) }
 
 // ServerPublicKey returns a ClientOpt to declare that the server's DERP public key is known.