Fix typo

src/bin/juliainstaller.rs

@@ -408,7 +408,7 @@ pub fn main() -> Result<()> {
  }
 
  if failed_paths.len() > 0 {
- println!("Juliaup needs to modify a number of existin files on your");
+ println!("Juliaup needs to modify a number of existing files on your");
  println!("system, but is unable to edit some of these files. Most likely");
  println!("this is caused by incorrect permissions on these files. The");
  println!("following files could not be edited:");