refactor(krun): remove the unused kvm_available probe

No caller: the CLI probes through kvm_probe, which reports the
failure mode instead of a boolean.

crates/ecrou/src/krun.rs

@@ -324,11 +324,6 @@ pub fn kvm_probe() -> Result<()> {
     Ok(())
 }
 
-/// True when a KVM probe passes; `ecrou probe` and tests use this.
-pub fn kvm_available() -> bool {
-    kvm_probe().is_ok()
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;