gnucash-docs stable: Replace list(POP_FRONT) with older iteration technique

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash-docs/commit/98d9d72d (commit)
	from  https://github.com/Gnucash/gnucash-docs/commit/ad6718b5 (commit)



commit 98d9d72d9e9762b11a0d91837dabb160e5c90f23
Author: John Ralls <jralls at ceridwen.us>
Date:   Mon Sep 11 11:37:49 2023 -0700

    Replace list(POP_FRONT) with older iteration technique
    
    To allow building with CMake < 3.15.



Summary of changes:
 cmake/AddGncDocTargets.cmake | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)