fix(deps): downgrade kotlinCoroutinesVersion from 1.7.1 to 1.6.4

This reverts commit 80b8ac9

Awala Ping doesn't yet support coroutines v1.7, so the build fails with:

```
Using 'asFlow(): Flow<T>' is an error. 'BroadcastChannel' is obsolete and all corresponding operators are deprecated in the favour of StateFlow and SharedFlow
```

build.gradle

@@ -1,7 +1,7 @@
 buildscript {
     ext {
         kotlinVersion = '1.8.21'
-        kotlinCoroutinesVersion = '1.7.1'
+        kotlinCoroutinesVersion = '1.6.4'
     }
     repositories {
         google()