Fix Neo4j reactive implementation

[mraible]

Fixes issue found when testing 8.2. #25259 (comment)

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[mraible]

The ms-mf-ng-consul-oauth2-neo4j job is failing with the following error after this change:

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'postRepository' defined in com.okta.developer.blog.repository.PostRepository defined in @EnableReactiveNeo4jRepositories declared on Neo4jReactiveRepositoriesRegistrar.EnableReactiveNeo4jRepositoriesConfiguration: Repository com.okta.developer.blog.repository.PostRepository implements org.springframework.data.repository.query.QueryByExampleExecutor but ReactiveNeo4jRepositoryFactory does not support Query by Example

I also noticed that the Spring Boot Maven Plugin needs a version specified.

Warning: Some problems were encountered while building the effective model for com.okta.developer.gateway:gateway:jar:8.1.0-git
Warning: 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: org.springframework.boot:spring-boot-configuration-processor:jar -> duplicate declaration of version (?) @ line 95, column 21
Warning: 'build.plugins.plugin.version' for org.springframework.boot:spring-boot-maven-plugin is missing. @ line 321, column 21

[mraible]

It looks like the spring-boot-configuration-processor plugin is listed twice in pom.xml too.

Update: Maven warnings are fixed in #25524.