neomutt: update to 20231221.

2023-12-21  Richard Russon  \<rich@flatcap.org\>
* Features
  - #4126 - add alias 'tags:'
* Bug Fixes
  - #4115 - create HelpBar after colours
  - #4116 - Fix Batch Sending of Emails
  - #4119 - Fix Header Cache Key Handling
  - #4121 - mutt_oauth2.py: error out if ENCRYPTION_PIPE was not supplied
  - #4124 - config: fix flag overlaps
  - #4125 - compose: restore view-text/pager/mailcap
  - color: fix attr_color_copy()
  - fix :color dump
  - fix leak in completion
  - force mail check on current mailbox after `<imap-fetch-mail>`
  - Allow sending an empty mail
  - mutt_oauth2.py: Use readline to overcome macOS input() restrictions
* Changed Config
  - add $history_format: '%s'
* Translations
  - 100% Czech
  - 100% German
  - 100% Lithuanian
  - 100% Serbian
  - 100% Slovak
  - 100% Turkish
  - 99% Spanish
  - 99% Hungarian
* Coverity defects
  - #4111 Educate Coverity about ARRAYs
  - fix defects
* Build
  - #4098 - build: use fallthrough attribute
  - #4100 - build: split maildir and mh types
  - #4101 - version: drop default features
  - #4108 - strip non-conditionals
  - #4122 - add github action to check for unused functions (xunused)
  - update fedora action
  - coverage: fix build for lcov v2
  - tests: fix error cases
* Code
  - #4097 - config: add DT_ON_STARTUP
  - #4104 - Change mutt_default_save() and addr_hook() to take a buffer
  - #4105 - Use buffer pool in tests
  - #4106 - Switch some buffers to use the buffer pool
  - #4109 - Improve the Progress Bar
  - #4117 - remove MxOps::path_parent() and mutt_path_parent()
  - #4120 - remove unused functions
  - #4131 - move editor test code
  - #4133 - move log_disp_null() into test folder
  - #4137 - move config string name functions into tests
  - add: hook_new()/hook_free()
  - fix more printf-style params
  - rename compare to equal
  - hcache: renaming for clarity


(wiz)