Revert "Add a reentrant lock to our entity data store."

I'm pretty sure this was causing the recent issues with tasks and events
disappearing as described in #97.

Regardless of this, it's not actually needed as SQLite on Android is
already thread-safe. The SQLite locks some users were experiencing were
probably fixed in 26ea890

This reverts commit 9ed172e.

app/src/main/java/com/etesync/syncadapter/model/MyEntityDataStore.kt

@@ -1,60 +1,9 @@
 package com.etesync.syncadapter.model
 
 import io.requery.Persistable
-import io.requery.meta.Attribute
 import io.requery.sql.Configuration
 import io.requery.sql.EntityDataStore
-import java.util.concurrent.locks.ReentrantLock
-import kotlin.concurrent.withLock
 
 class MyEntityDataStore(configuration: Configuration): EntityDataStore<Persistable>(configuration) {
-    val lock = ReentrantLock()
 
-    override fun <K : Any?, E : Persistable?> insert(entity: E, keyClass: Class<K>?): K {
-        lock.withLock {
-            return super.insert(entity, keyClass)
-        }
-    }
-
-    override fun <E : Persistable?> update(entity: E): E {
-        lock.withLock {
-            return super.update(entity)
-        }
-    }
-
-    override fun <E : Persistable?> update(entity: E, vararg attributes: Attribute<*, *>?): E {
-        lock.withLock {
-            return super.update(entity, *attributes)
-        }
-    }
-
-    override fun <E : Persistable?> upsert(entity: E): E {
-        lock.withLock {
-            return super.upsert(entity)
-        }
-    }
-
-    override fun <E : Persistable?> refresh(entity: E): E {
-        lock.withLock {
-            return super.refresh(entity)
-        }
-    }
-
-    override fun <E : Persistable?> refresh(entity: E, vararg attributes: Attribute<*, *>?): E {
-        lock.withLock {
-            return super.refresh(entity, *attributes)
-        }
-    }
-
-    override fun <E : Persistable?> refreshAll(entity: E): E {
-        lock.withLock {
-            return super.refreshAll(entity)
-        }
-    }
-
-    override fun <E : Persistable?> delete(entity: E): Void {
-        lock.withLock {
-            return super.delete(entity)
-        }
-    }
 }