fix publish github action pipeline about mat-datetimepicker

[bbortt]

that pipeline is so clean @kuhnroyal.. I almost can't get over it!

will also deliver a fix for pages in a second..

[bbortt]

tagging and version bump works, so I assume at least the ACTION_TOKEN is fine (used for pushing).
for now I've still manually released v9.0.0 and v9.0.1.

[bbortt]

fix delivered in: #193 - v9.0.2. action: https://github.com/kuhnroyal/mat-datetimepicker/runs/4648865288?check_suite_focus=true.

[bbortt]

GH pages deployment resolved in #198 (v9.0.13). corresponding action: https://github.com/kuhnroyal/mat-datetimepicker/actions/runs/1631647557.