clippy: fix useless_conversion lint

https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion

Author: xtqqczze

src/uu/dd/src/dd.rs

@@ -568,7 +568,7 @@ impl Input<'_> {
                     bytes_total += rlen;
                     reads_partial += 1;
                     let padding = vec![pad; target_len - rlen];
-                    buf.splice(base_idx + rlen..next_blk, padding.into_iter());
+                    buf.splice(base_idx + rlen..next_blk, padding);
                 }
                 rlen => {
                     bytes_total += rlen;

src/uu/dircolors/src/dircolors.rs

@@ -364,7 +364,7 @@ where
     let mut state = ParseState::Global;
     let mut saw_colorterm_match = false;
 
-    for (num, line) in (1..).zip(user_input.into_iter()) {
+    for (num, line) in (1..).zip(user_input) {
         let line = line.borrow().purify();
         if line.is_empty() {
             continue;

src/uu/od/src/parse_formats.rs

@@ -121,7 +121,7 @@ pub fn parse_format_flags(args: &[String]) -> Result<Vec<ParsedFormatterItemInfo
     for arg in arg_iter {
         if expect_type_string {
             let v = parse_type_string(arg)?;
-            formats.extend(v.into_iter());
+            formats.extend(v);
             expect_type_string = false;
         } else if arg.starts_with("--") {
             if arg.len() == 2 {
@@ -130,7 +130,7 @@ pub fn parse_format_flags(args: &[String]) -> Result<Vec<ParsedFormatterItemInfo
             if arg.starts_with("--format=") {
                 let params: String = arg.chars().skip_while(|c| *c != '=').skip(1).collect();
                 let v = parse_type_string(&params)?;
-                formats.extend(v.into_iter());
+                formats.extend(v);
             }
             if arg == "--format" {
                 expect_type_string = true;
@@ -154,7 +154,7 @@ pub fn parse_format_flags(args: &[String]) -> Result<Vec<ParsedFormatterItemInfo
             }
             if !format_spec.is_empty() {
                 let v = parse_type_string(&format_spec)?;
-                formats.extend(v.into_iter());
+                formats.extend(v);
                 expect_type_string = false;
             }
         }