Use apt-provided python for trust store conversion

Author: schiermi

.github/workflows/ci.yml

@@ -98,7 +98,7 @@ jobs:
         cd src/truststore/
         curl --remote-name https://raw.githubusercontent.com/espressif/arduino-esp32/master/tools/gen_crt_bundle.py
         curl --remote-name https://curl.se/ca/cacert.pem
-        python3 gen_crt_bundle.py --input cacert.pem
+        /usr/bin/python3 gen_crt_bundle.py --input cacert.pem
 
     - name: Build firmware
       run: |