fix: instruct to resolve conflicts

When the cherr-picking failed, it's very likely that there are
conflicts. We should instruct the user to cherry-pick locally and
resolve any conflicts.

src/backport.ts

@@ -404,7 +404,7 @@ export class Backport {
     );
     return dedent`Backport failed for \`${target}\`, ${reason}.
 
-                  Please cherry-pick the changes locally.
+                  Please cherry-pick the changes locally and resolve any conflicts.
                   ${suggestion}`;
   }