linux: add truststore as a dependency

Because Linux distributions don't have an 'universal' path for the
system certificate store, bundling libssl built on distro A might not
work on distro B, because distros tend to change path to the
certificate store at build time.

This means that creating a PyInstaller package on Ubuntu will include
the libssl built there, and if you try to run this package on a
different distro (e.g. Arch Linux), any attempt to create an SSL
connection will fail, because Arch Linux has a different path for the
certificate store than Ubuntu.

This issue is usually worked around by bundling certificates with the
app (usually using certifi), and then pointing the SSL_CERT_FILE
environment to it.

However, truststore seems to be a better alternative, since it tries to
use the certificate store from the system instead.

The list of benefits are listed on the project's page on GitHub:

https://github.com/sethmlarson/truststore

requirements.txt

@@ -7,3 +7,4 @@ PyGObject; sys_platform == "linux" # required for better system tray support on
 # undetected-chromedriver
 # this is installed only on windows
 pywin32; sys_platform == "win32"
+truststore; sys_platform == "linux" and python_version >= "3.10"