docs(functions): drop backticks from doc-headers

CONTRIBUTING states doc-headers are written as plain text -- the header
is read as-is by config-help, by funcsave, and by anyone opening the
file, and docs/codespans.py adds the site's inline code spans at render
time. 22 files had drifted from that, carrying 41 hand-written spans
that reached config-help and the man page as literal backtick
characters inside an otherwise verbatim block.

The one span whose content ended in a space is requoted rather than
dropped, so "read> " keeps reading as a prompt string.

functions/__fish_user_dots_link.fish

@@ -8,7 +8,7 @@
 #   __fish_user_dots_link
 #
 # DESCRIPTION
-#   Manages the git-ignored `user-dots` convenience symlink in the fish config
+#   Manages the git-ignored user-dots convenience symlink in the fish config
 #   directory ($__fish_config_dir/user-dots), pointing it at the resolved
 #   $__fish_user_dots_path so the private overlay can be browsed from
 #   ~/.config/fish/.