Removed unused links

Author: javiereguiluz

doctrine.rst

@@ -875,13 +875,11 @@ Learn more
 
 .. _`Doctrine`: http://www.doctrine-project.org/
 .. _`RFC 3986`: https://www.ietf.org/rfc/rfc3986.txt
-.. _`MongoDB`: https://www.mongodb.org/
 .. _`Doctrine's Mapping Types documentation`: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/basic-mapping.html
 .. _`Query Builder`: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/query-builder.html
 .. _`Doctrine Query Language`: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/dql-doctrine-query-language.html
 .. _`Reserved SQL keywords documentation`: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/basic-mapping.html#quoting-reserved-words
 .. _`DoctrineMongoDBBundle docs`: https://symfony.com/doc/current/bundles/DoctrineMongoDBBundle/index.html
-.. _`DoctrineMongoDBBundle`: https://symfony.com/doc/current/bundles/DoctrineMongoDBBundle/index.html
 .. _`DoctrineFixturesBundle`: https://symfony.com/doc/current/bundles/DoctrineFixturesBundle/index.html
 .. _`Transactions and Concurrency`: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/transactions-and-concurrency.html
 .. _`DoctrineMigrationsBundle`: https://github.com/doctrine/DoctrineMigrationsBundle