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/qc.fish

@@ -15,7 +15,7 @@
 #   scripts/cli-agent.md to $XDG_CONFIG_HOME/aichat/roles/cli.md. Inherits
 #   every aichat flag and tab completion (--wraps aichat); passing --role/-r
 #   overrides the default role, so qc forwards to aichat unchanged. The
-#   function is only defined when aichat is installed. Run `qc --help` for
+#   function is only defined when aichat is installed. Run qc --help for
 #   aichat's full flag reference with the command name rewritten to qc.
 #
 # ARGUMENTS