chore: fix pre-existing clippy::question_mark lints in indexes and iterators

Author: EbrahimEldesoky

src/indexes.rs

@@ -57,10 +57,7 @@ where D: Dimension
     #[inline]
     fn next(&mut self) -> Option<Self::Item>
     {
-        let index = match self.index {
-            None => return None,
-            Some(ref ix) => ix.clone(),
-        };
+        let index = self.index.as_ref()?.clone();
         self.index = self.dim.next_for(index.clone());
         Some(index.into_pattern())
     }

src/iterators/mod.rs

@@ -512,10 +512,7 @@ impl<'a, A, D: Dimension> Iterator for IndexedIter<'a, A, D>
     #[inline]
     fn next(&mut self) -> Option<Self::Item>
     {
-        let index = match self.0.inner.index {
-            None => return None,
-            Some(ref ix) => ix.clone(),
-        };
+        let index = self.0.inner.index.as_ref()?.clone();
         match self.0.next() {
             None => None,
             Some(elem) => Some((index.into_pattern(), elem)),
@@ -695,10 +692,7 @@ impl<'a, A, D: Dimension> Iterator for IndexedIterMut<'a, A, D>
     #[inline]
     fn next(&mut self) -> Option<Self::Item>
     {
-        let index = match self.0.inner.index {
-            None => return None,
-            Some(ref ix) => ix.clone(),
-        };
+        let index = self.0.inner.index.as_ref()?.clone();
         match self.0.next() {
             None => None,
             Some(elem) => Some((index.into_pattern(), elem)),