Subresource collection filters not added by DocumentationNormalizer

[YaoOcelotl]

Hi.

The DocumentationNormalizer is using the wrong resource class for obtaining subresource collection filters.
In DocumentationNormalizer.php#L157 uses the parent resource class

if ($parameters = $this->getFiltersParameters($resourceClass, $operationName, $subResourceMetadata, $definitions, $serializerContext)) {

it should use the subresource class

if ($parameters = $this->getFiltersParameters($subresourceOperation['resource_class'], $operationName, $subResourceMetadata, $definitions, $serializerContext)) {

[soyuka]

Again linked to #1617 #1616 #1612 #1649

#1612 (comment)

[soyuka]

Closing in favor of #2706