pgsql: Remove traces of version-0 calling convention in src/tutorial/

Remove traces of version-0 calling convention in src/tutorial/

Support has been removed as of 5ded4bd, but code related to the tutorial
still used it.  Functions using version-1 are already present for some
time in the tutorial, and the documentation mentions them, so just
replace the old version with the new one.

Reported-by: Pavel Stehule
Analyzed-by: Euler Taveira
Author: Michael Paquier
Reviewed-by: Tom Lane, Pavel Stehule
Discussion: https://postgr.es/m/CAFj8pRCgC2uDzrw-vvanXu6Z3ofyviEOQPEpH6_aL4OCe7JRag@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a9d5157ae8a7680b496d56f4edc3a43feff708c4

Modified Files
--------------
src/tutorial/funcs.c     | 107 ++++++++++++++++++++++-----------------
src/tutorial/funcs_new.c | 129 -----------------------------------------------
2 files changed, 61 insertions(+), 175 deletions(-)