BUG #17939: CREATE EXTENSION pltcl; looks in the wrong folder

The following bug has been logged on the website:

Bug reference: 17939
Logged by: Matthew Baynham
Email address: matthew.baynham@gmail.com
PostgreSQL version: 15.2
Operating system: Ubuntu 2304
Description:

I install pltcl with the following command...
sudo apt-get install postgresql-pltcl

Then I need to create the extension with...
CREATE EXTENSION pltcl;

So now I have version 15.2 of PostgreSQL and the apt-get command did it's
job correctly and installed into...
matthew@matthew-QEMU:~$ cd "/usr/share/postgresql/15/extension"
matthew@matthew-QEMU:/usr/share/postgresql/15/extension$ ls plt*
pltcl--1.0.sql pltcl.control pltclu--1.0.sql pltclu.control

However the create extension command is looking in the wrong folder.
matthew@matthew-QEMU:~$ psql -d matthew -U matthew
psql (15.2 (Ubuntu 15.2-1), server 14.7 (Ubuntu 14.7-0ubuntu0.22.10.1))
Type "help" for help.

matthew=# CREATE EXTENSION pltcl;
ERROR: could not open extension control file
"/usr/share/postgresql/14/extension/pltcl.control": No such file or
directory

So when the version I have is definitely version 15.2 it looks for
extensions in the folder for version 14.