Server(fix[confirm_before,command_prompt]): -b requires tmux 3.3+, not 3.4+

why: The -b flag for confirm-before and command-prompt was added in
tmux 3.3, not 3.4. Verified across version worktrees: tmux-3.2a has
args "p:t:" while tmux-3.3 has "bp:t:".
what:
- Change "Requires tmux 3.4+" to "Requires tmux 3.3+" in both docstrings

Author: tony

src/libtmux/server.py

@@ -840,7 +840,7 @@ def confirm_before(
         Always uses ``-b`` (background) to avoid blocking the command queue.
         Use ``send-keys -K -c <client>`` to provide the confirmation key.
 
-        Requires tmux 3.4+ for ``-b`` flag support.
+        Requires tmux 3.3+ for ``-b`` flag support.
 
         Parameters
         ----------
@@ -905,7 +905,7 @@ def command_prompt(
         Always uses ``-b`` (background) to avoid blocking the command queue.
         Use ``send-keys -K -c <client>`` to type into the prompt and submit.
 
-        Requires tmux 3.4+ for ``-b`` flag support.
+        Requires tmux 3.3+ for ``-b`` flag support.
 
         Parameters
         ----------