templates: drop unused coding info from all templates

[rmilecki]

For some unkown reason early templates contained line like:
    # -*- coding: utf-8 -*-

It seems to be unused. It doesn't belong to YAML specification. It seems
like a copy & paste mistake from Python source file.

Remove all those unused lines. All YAML templates as expected to be
UTF-8 encoded anyway.

Those changes were automatically generated using:
sed -i '/coding:/d' src/invoice2data/extract/templates/*/*.yml
find ./tests/custom/ -name "*.yml" -exec sed -i '/coding:/d' {} \;

[rmilecki]

Discovered in the #445 (comment)