fix safety hint

src/main.rs

@@ -3,11 +3,11 @@ use memmap2::MmapOptions;
 
 fn main() {
     let file = std::fs::File::open("measurements.txt").unwrap();
-    // SAFETY: we are not going to modify the file while the program is running. No lock required
-    // for now.
 
     let mut datas = vec![];
 
+    // SAFETY: we are not going to modify the file while the program is running. No lock required
+    // for now.
     let mmap = unsafe { MmapOptions::new().map(&file) }.unwrap();
     mmap.advise(memmap2::Advice::Sequential).unwrap();