update core - revert rust toolchain to v. 1.64.0

deltachat-ios/libraries/deltachat-core-rust

@@ -1 +1 @@
-Subproject commit aa6f5fd139e7eb77b59abc055b38c1a0bfccde52
+Subproject commit 5922fb38da885c005d746b6ae09247ba2e96e2c6