chore: update rust version

Author: mootz12

Cargo.toml

@@ -22,7 +22,7 @@ exclude = [
 
 [workspace.package]
 version = "25.2.0"
-rust-version = "1.89.0"
+rust-version = "1.91.0"
 
 # Dependencies located in this repo:
 [workspace.dependencies.soroban-cli]