chore: make it compile with Rust 1.71 (#128)

The current version won't compile with Rust 1.71:

    error: unnecessary qualification
        --> src/merkle.rs:2021:17
         |
    2021 |     iter: <I as std::iter::IntoIterator>::IntoIter,
         |                 ^^^^^^^^^^^^^^^^^^^^^^^
         |
    note: the lint level is defined here
        --> src/lib.rs:72:5
         |
    72   |     unused_qualifications,
         |     ^^^^^^^^^^^^^^^^^^^^^

    error: could not compile `merkletree` (lib) due to previous error

This commit fixes that error.

src/merkle.rs

@@ -2018,7 +2018,7 @@ pub fn populate_data<
     I: IntoIterator<Item = Result<E>>,
 >(
     data: &mut S,
-    iter: <I as std::iter::IntoIterator>::IntoIter,
+    iter: I::IntoIter,
 ) -> Result<()> {
     if !data.is_empty() {
         return Ok(());