resource/aws_ssm_patch_group: Fix gosimple linting issues
resource/aws_ssm_patch_group: Fix gosimple linting issues

Previously:

```
aws/resource_aws_ssm_patch_group.go:90:2:warning: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013) (gosimple)
```

Output from acceptance testing:

```
--- PASS: TestAccAWSSSMPatchGroup_basic (12.45s)
```

terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,Ninir/terraform-provider-aws,terraform-providers/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,Ninir/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws