gCI: activate tParallel linter

.golangci.yml

Makefile

engines/mjml/mjml_test.go

engines/mustache/engine_test.go

engines/wpd/process_test.go

engines/wpd/wpd_test.go

lib/condchan_test.go

models/template_db_test.go

restapi/handlers/account-template-update_test.go

restapi/handlers/renderlogs_test.go

restapi/handlers/user-get_test.go

restapi/handlers/user-list_test.go

restapi/handlers/user-update_test.go

utils/parse_period_test.go