Update bitcoin-kmp (#839)

To add support for P2A PSBTs.

Author: t-bast

gradle/libs.versions.toml

@@ -4,7 +4,7 @@ kotlinx-coroutines = "1.10.2"
 kotlinx-datetime = "0.7.1"
 kotlinx-serialization = "1.9.0"
 ktor = "3.3.0"
-bitcoinkmp = "0.28.0" # when upgrading bitcoin-kmp, keep secpjnijvm in sync!
+bitcoinkmp = "0.28.1" # when upgrading bitcoin-kmp, keep secpjnijvm in sync!
 secpjnijvm = "0.21.0"
 kermit = "2.0.8"
 slf4j = "2.0.17"