Upgrade H2 to latest version

mailbox-core/build.gradle

@@ -27,7 +27,7 @@ dependencies {
     implementation "io.ktor:ktor-jackson:$ktor_version"
     api "org.slf4j:slf4j-api:1.7.32"
 
-    implementation 'com.h2database:h2:1.4.192' // The last version that supports Java 1.6
+    implementation 'com.h2database:h2:1.4.200'
 
     // Base 32
     implementation 'dev.keiji.rfc4648:rfc4648:1.0.0'

mailbox-core/src/main/java/org/briarproject/mailbox/core/db/H2Database.kt

@@ -33,7 +33,7 @@ open class H2Database(
     }
 
     private val dbPath: String get() = File(config.getDatabaseDirectory(), "db").absolutePath
-    private val url: String = ("jdbc:h2:split:$dbPath;MULTI_THREADED=1;WRITE_DELAY=0")
+    private val url: String = ("jdbc:h2:split:$dbPath;WRITE_DELAY=0")
 
     override fun open(listener: MigrationListener?): Boolean {
         val dir = config.getDatabaseDirectory()