Executions dont switch owner (#326)

when an building is taken over by another player the execution for it
doesnt change its owner this makes it so when a sam is captured it tries
to intercept your own nukes and doesnt intercept the ones by the
previous player

this change makes executions of buildings automaticly switch their owner

src/core/execution/ShellExecution.ts

@@ -63,9 +63,6 @@ export class ShellExecution implements Execution {
     }
   }
 
-  owner(): Player {
-    return null;
-  }
   isActive(): boolean {
     return this.active;
   }