chore: Fix docs/snippets exposed-dao project build fail

- Replace experimental kotlin.io.encoding.Base64 with stable java.util.Base64

documentation-website/Writerside/snippets/exposed-dao/src/main/kotlin/org/example/entities/EntityWithBase64.kt

@@ -4,21 +4,19 @@ import org.jetbrains.exposed.dao.IntEntity
 import org.jetbrains.exposed.dao.IntEntityClass
 import org.jetbrains.exposed.dao.id.EntityID
 import org.jetbrains.exposed.dao.id.IntIdTable
-import kotlin.io.encoding.Base64
-import kotlin.io.encoding.ExperimentalEncodingApi
+import java.util.Base64
 
 object TableWithText : IntIdTable() {
     val text = varchar("text", length = 2048)
 }
 
 class EntityWithBase64(id: EntityID<Int>) : IntEntity(id) {
-    @OptIn(ExperimentalEncodingApi::class)
     var base64: String by TableWithText.text
         .memoizedTransform(
-            wrap = { Base64.encode(it.toByteArray()) },
-            unwrap = { Base64.decode(it).toString() }
+            wrap = { Base64.getEncoder().encodeToString(it.toByteArray()) },
+            unwrap = { Base64.getDecoder().decode(it).toString() }
         )
 
     companion object :
-        IntEntityClass<EntityWithUInt>(TableWithText)
+        IntEntityClass<EntityWithBase64>(TableWithText)
 }