Update dependency io.reactivex.rxjava3:rxjava to v3.1.8

Author: renovate[bot]

app/build.gradle.kts

@@ -99,7 +99,7 @@ dependencies {
     implementation("com.squareup.okhttp3:logging-interceptor:4.11.0")
     implementation("com.squareup.okhttp3:okhttp:4.11.0")
     implementation("com.google.code.gson:gson:2.10.1")
-    implementation("io.reactivex.rxjava3:rxjava:3.1.6")
+    implementation("io.reactivex.rxjava3:rxjava:3.1.8")
     implementation("io.reactivex.rxjava3:rxkotlin:3.0.1")
     implementation("io.reactivex.rxjava3:rxandroid:3.0.2")