tests/provider: Enable tfproviderlint R002 check (#12033)

Reference: #9952

Previously:

```
aws/resource_aws_sns_platform_application.go:230:18: R002: ResourceData.Set() pointer value dereference is extraneous
```

We are unable to acceptance test the `aws_sns_platform_application` resource as it requires an active Apple Developer subscription and application, however this final refactor is trivial.

GNUmakefile

@@ -69,6 +69,7 @@ lint:
  -AT006 \
  -AT007 \
  -AT008 \
+ -R002 \
  -R004 \
  -R006 \
  -R012 \

aws/resource_aws_sns_platform_application.go

@@ -225,9 +225,9 @@ func resourceAwsSnsPlatformApplicationRead(d *schema.ResourceData, meta interfac
  // Some of the fetched attributes are stateful properties such as
  // the number of subscriptions, the owner, etc. skip those
  if resource.Schema[iKey] != nil {
- value := *attrmap[oKey]
+ value := aws.StringValue(attrmap[oKey])
  log.Printf("[DEBUG] Updating %s => %s -> %s", iKey, oKey, value)
- d.Set(iKey, *attrmap[oKey])
+ d.Set(iKey, value)
  }
  }
  }