doc: release-notes: Fix typo in networking part

Fix typo in networking part of the release notes.

Signed-off-by: Robert Lubos <[email protected]>

Author: rlubos

doc/releases/release-notes-3.4.rst

@@ -973,7 +973,7 @@ Networking
   * Fixed missing token length validation in :c:func:`coap_header_get_token`.
   * Fixed missing response check in :c:func:`coap_response_received`.
 
-* Connection Manger:
+* Connection Manager:
 
   * Extended the library with a generic L2 connectivity API.
   * Refactored library internals significantly.