Update hard-coded versions for sync with Emacs

doc/orgcard.tex

@@ -1,5 +1,5 @@
 % Reference Card for Org Mode
-\def\orgversionnumber{9.6.15}
+\def\orgversionnumber{9.6.19}
 \def\versionyear{2023}          % latest update
 \input emacsver.tex
 

lisp/org-version.el

@@ -5,13 +5,13 @@
 (defun org-release ()
   "The release version of Org.
 Inserted by installing Org mode or when a release is made."
-   (let ((org-release "9.6.15"))
+   (let ((org-release "9.6.19"))
      org-release))
 ;;;###autoload
 (defun org-git-version ()
   "The Git version of Org mode.
 Inserted by installing Org or when a release is made."
-   (let ((org-git-version "release_9.6.15"))
+   (let ((org-git-version "release_9.6.19"))
      org-git-version))
 
 (provide 'org-version)