docs(CHANGES): Remove final 'hydration' jargon

why: "hydration" is an internal mental model — users see the
result, not the query mechanic.

what: Replace 'hydration query' with 'initialization query' in
the 0.53.1 entry.

Author: tony

CHANGES

@@ -555,7 +555,7 @@ surface from Make to Just.
 
 ### Fixes
 
-#### `Server.new_session()` no longer races its own hydration query (#625)
+#### `Server.new_session()` no longer races its own initialization query (#625)
 
 {meth}`~libtmux.Server.new_session` now parses all required session fields from
 the `tmux new-session -P` output instead of creating the session and then