Simplify find_crlf

This is both simpler to read and compiles to better code:
https://rust.godbolt.org/z/MxKodv

crates/rust-analyzer/src/line_endings.rs

@@ -46,7 +46,7 @@ impl LineEndings {
         return (src, LineEndings::Dos);
 
         fn find_crlf(src: &[u8]) -> Option<usize> {
-            src.iter().zip(src.iter().skip(1)).position(|it| it == (&b'\r', &b'\n'))
+            src.windows(2).position(|it| it == b"\r\n")
         }
     }
 }