fix(example): Use kotlin version compatible with AGP8

[Gustl22]

Description

Use kotlin version which is compatible with AGP8.

See https://github.com/bluefireteam/audioplayers/actions/runs/5616959780/job/15220225951 :

e: /home/runner/work/audioplayers/audioplayers/packages/audioplayers/example/build/audioplayers_android/.transforms/b8ec2b7f9edecdc552d5b724ef88efef/transformed/out/jars/classes.jar!/META-INF/audioplayers_android_release.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.9.0, expected version is 1.7.1.
e: /home/runner/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.9.0/8ee15ef0c67dc83d874f412d84378d7f0eb50b63/kotlin-stdlib-1.9.0.jar!/META-INF/kotlin-stdlib.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.9.0, expected version is 1.7.1.
e: /home/runner/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.9.0/8ee15ef0c67dc83d874f412d84378d7f0eb50b63/kotlin-stdlib-1.9.0.jar!/META-INF/kotlin-stdlib-jdk8.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.9.0, expected version is 1.7.1.
e: /home/runner/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.9.0/8ee15ef0c67dc83d874f412d84378d7f0eb50b63/kotlin-stdlib-1.9.0.jar!/META-INF/kotlin-stdlib-jdk7.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.9.0, expected version is 1.7.1.
e: /home/runner/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-common/1.9.0/cd65c21cfd1eec4d44ef09f9f52b6d9f8a720636/kotlin-stdlib-common-1.9.0.jar!/META-INF/kotlin-stdlib-common.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.9.0, expected version is 1.7.1.
ERROR: Missing classes detected while running R8. Please add the missing classes or apply additional keep rules that are generated in /home/runner/work/audioplayers/audioplayers/packages/audioplayers/example/build/app/outputs/mapping/release/missing_rules.txt.
ERROR: R8: Missing class org.kxml2.io.KXmlParser,org.kxml2.io.KXmlSerializer (referenced from: java.util.List kotlinx.coroutines.internal.FastServiceLoader.load(java.lang.Class, java.lang.ClassLoader))

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, refactor:,
  docs:, chore:, test:, ci: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation and added dartdoc comments with ///, where necessary.
• I have updated/added relevant examples in example.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

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