Fix monitor schema in framework implementation

[tosuke]

In SDK implementation, mackerel_monitor.anomaly_detection.scopes is required:

terraform-provider-mackerel/mackerel/resource_mackerel_monitor.go

Lines 332 to 336 in 7586ebb

	"scopes": {
	Type: schema.TypeSet,
	Required: true,
	Elem: &schema.Schema{Type: schema.TypeString},
	},

But in framework implementation, it is a optional attribute. This PR makes it required.

Output from acceptance testing:

$ make testacc TESTS='AccMackerelMonitor'
TF_ACC=1 go test -v ./... -run AccMackerelMonitor -timeout 120m
?       github.com/mackerelio-labs/terraform-provider-mackerel  [no test files]
testing: warning: no tests to run
PASS
ok      github.com/mackerelio-labs/terraform-provider-mackerel/internal/mackerel        0.277s [no tests to run]
testing: warning: no tests to run
PASS
ok      github.com/mackerelio-labs/terraform-provider-mackerel/internal/planmodifierutil        0.426s [no tests to run]
testing: warning: no tests to run
PASS
ok      github.com/mackerelio-labs/terraform-provider-mackerel/internal/provider        0.795s [no tests to run]
testing: warning: no tests to run
PASS
ok      github.com/mackerelio-labs/terraform-provider-mackerel/internal/typeutil        0.454s [no tests to run]
testing: warning: no tests to run
PASS
ok      github.com/mackerelio-labs/terraform-provider-mackerel/internal/validatorutil   0.282s [no tests to run]
=== RUN   TestAccMackerelMonitor_HostMetric
=== PAUSE TestAccMackerelMonitor_HostMetric
=== RUN   TestAccMackerelMonitor_Connectivity
=== PAUSE TestAccMackerelMonitor_Connectivity
=== RUN   TestAccMackerelMonitor_ServiceMetric
=== PAUSE TestAccMackerelMonitor_ServiceMetric
=== RUN   TestAccMackerelMonitor_External
=== PAUSE TestAccMackerelMonitor_External
=== RUN   TestAccMackerelMonitor_Expression
=== PAUSE TestAccMackerelMonitor_Expression
=== RUN   TestAccMackerelMonitor_AnomalyDetection
=== PAUSE TestAccMackerelMonitor_AnomalyDetection
=== RUN   TestAccMackerelMonitor_Query
=== PAUSE TestAccMackerelMonitor_Query
=== CONT  TestAccMackerelMonitor_HostMetric
=== CONT  TestAccMackerelMonitor_Expression
=== CONT  TestAccMackerelMonitor_Query
=== CONT  TestAccMackerelMonitor_ServiceMetric
=== CONT  TestAccMackerelMonitor_Connectivity
=== CONT  TestAccMackerelMonitor_External
=== CONT  TestAccMackerelMonitor_AnomalyDetection
--- PASS: TestAccMackerelMonitor_Expression (5.87s)
--- PASS: TestAccMackerelMonitor_ServiceMetric (6.21s)
--- PASS: TestAccMackerelMonitor_HostMetric (6.50s)
--- PASS: TestAccMackerelMonitor_Connectivity (6.51s)
--- PASS: TestAccMackerelMonitor_Query (6.54s)
--- PASS: TestAccMackerelMonitor_AnomalyDetection (6.55s)
--- PASS: TestAccMackerelMonitor_External (6.61s)
PASS
ok      github.com/mackerelio-labs/terraform-provider-mackerel/mackerel 7.746s
...

[ne-sachirou]

🙆‍♀️