Fix version free entity matching

[adatzer]

In Snowplow Entities to Add/Edit mapping, when Apply to all versions is set to True, matching allows for com_acme_test_1 to match com_acme_test_me_1.

Steps to reproducible example:

1. Construct event payload with entities: com_acme_product_1 and com_acme_product_entity_1
2. Set as entities rules:

{
      key: 'iglu:com.acme/product/jsonschema/1-5-0',
      mappedKey: 'something',
      propertiesObjectToPopulate: 'event_object',
      version: 'free',
},

The bug is that while iterating through the entities of the event, the com_acme_product_entity_1 will wrongly match the version-free com_acme_product