chore(tvix/docs): Small changes to Nix Daemon protocol description

I found some more operations that are obsolete and a few missing
fields. I also did some small changes to make handshake description
more consistent.

Change-Id: I9f853a37e9d50621491f31ea71879d6a600046e2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12724
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/docs/src/nix-daemon/handshake.md

@@ -3,7 +3,7 @@
 ## client -> server
 - 0x6e697863 :: [Int](#int) (hardcoded, 'nixc' in ASCII)
 
-## server -> client
+## client <- server
 - 0x6478696f :: [Int](#int) (hardcoded, 'dxio' in ASCII)
 - protocolVersion :: [Int](#int)
 
@@ -19,7 +19,7 @@
 - reserveSpace :: [Bool](#bool) (obsolete, ignored and set to false)
 
 
-## server -> client
+## client <- server
 
 ### If clientVersion is 1.33 or later
 - nixVersion :: String
@@ -27,6 +27,6 @@
 ### If clientVersion is 1.35 or later
 - trusted :: OptTrusted
 
-## server -> client
+## client <- server
 - send logs
 - [operation](./operations.md) :: Int