Gradle snippet update (#88)

# Pull Request Info

[PR Reviewing
Guidelines](https://github.com/mongodb/docs-java/blob/master/REVIEWING.md)

Per Slack convo, the coroutine library is a runtime dependency and can
be removed from the Gradle snippet

JIRA - no jira
Staging -
https://docs-mongodbcom-staging.corp.mongodb.com/kotlin/docsworker-xlarge/dependency-update/quick-start/

## Self-Review Checklist

- [ ] Is this free of any warnings or errors in the RST?
- [ ] Did you run a spell-check?
- [ ] Did you run a grammar-check?
- [ ] Are all the links working?

Author: cbullinger

source/includes/kotlin-driver-coroutine-gradle-versioned.rst

@@ -4,5 +4,4 @@
 
    dependencies {
        implementation("org.mongodb:mongodb-driver-kotlin-coroutine:{+full-version+}")
-       implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:+")
    }