Use = assignment syntax for a repository's url

Setting a property with the Gradle-generated propName value syntax is deprecated since Gradle 8.14 and scheduled for removal in Gradle 10. This recipe turns url 'x' into url = 'x' directly inside a maven { } or ivy { } block of repositories, in Groovy scripts. It stays out of every other block: a url in a builder closure such as pom.withXml { asNode().children().last() + { url 'x' } } is a call that adds an XML node, and fails as an assignment. Kotlin has no such syntax. See the Gradle 8.14 upgrade guide for more information.