Address: Support hours should be required in the plan if the incident_urgency_rule type is "use_support_hours"

[imjaroiswebdev]

Closes #843

Acceptance tests expanded...

==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test $(go list ./... |grep -v 'vendor') -v -count=1 -run TestAccPagerDutyService_FormatValidation -timeout 120m
?       github.com/PagerDuty/terraform-provider-pagerduty       [no test files]
=== RUN   TestAccPagerDutyService_FormatValidation
--- PASS: TestAccPagerDutyService_FormatValidation (40.49s)
PASS
ok      github.com/PagerDuty/terraform-provider-pagerduty/pagerduty     41.228s
testing: warning: no tests to run
PASS
ok      github.com/PagerDuty/terraform-provider-pagerduty/pagerdutyplugin       0.616s [no tests to run]
testing: warning: no tests to run
PASS
ok      github.com/PagerDuty/terraform-provider-pagerduty/util  0.714s [no tests to run]