fix warnings

[xuwei-k]

[warn] -- Deprecation Warning: /Users/runner/work/flyway-sbt/flyway-sbt/src/main/scala/flywaysbt/FlywayPlugin.scala:240:25 
[warn] 240 |      flywayResolvers := Array.empty[String],
[warn]     |                         ^
[warn]     |method copyArrayToImmutableIndexedSeq in class LowPriorityImplicits2 is deprecated since 2.13.0: implicit conversions from Array to immutable.IndexedSeq are implemented by copying; use `toIndexedSeq` explicitly if you want to copy, or use the more efficient non-copying ArraySeq.unsafeWrapArray

[warn] -- Deprecation Warning: /Users/runner/work/flyway-sbt/flyway-sbt/src/main/scala/flywaysbt/FlywayPlugin.scala:253:25 
[warn] 253 |      flywayCallbacks := new Array[Callback](0),
[warn]     |                         ^
[warn]     |method copyArrayToImmutableIndexedSeq in class LowPriorityImplicits2 is deprecated since 2.13.0: implicit conversions from Array to immutable.IndexedSeq are implemented by copying; use `toIndexedSeq` explicitly if you want to copy, or use the more efficient non-copying ArraySeq.unsafeWrapArray