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/repo-open.fish

@@ -12,7 +12,7 @@
 #   repo-open --help
 #
 # DESCRIPTION
-#   Opens the web page for the current repository's `origin` remote in a
+#   Opens the web page for the current repository's origin remote in a
 #   browser (via open-url). Deep-links to the current branch when it exists
 #   on the remote, falling back to the remote's default branch (main/master)
 #   otherwise, and to the current sub-directory when invoked below the repo