Fix a typo in the docs (#47391)

Just a docs text change.

packages/flutter/lib/src/rendering/box.dart

@@ -1313,8 +1313,7 @@ abstract class RenderBox extends RenderObject {
   /// function couples the child with the parent so that when the child's layout
   /// changes, the parent is notified (via [markNeedsLayout]).
   ///
-  /// Calling this function is expensive and as it can result in O(N^2)
-  /// behavior.
+  /// Calling this function is expensive as it can result in O(N^2) behavior.
   ///
   /// Do not override this method. Instead, implement [computeMinIntrinsicWidth].
   @mustCallSuper
@@ -1453,8 +1452,7 @@ abstract class RenderBox extends RenderObject {
   /// function couples the child with the parent so that when the child's layout
   /// changes, the parent is notified (via [markNeedsLayout]).
   ///
-  /// Calling this function is expensive and as it can result in O(N^2)
-  /// behavior.
+  /// Calling this function is expensive as it can result in O(N^2) behavior.
   ///
   /// Do not override this method. Instead, implement
   /// [computeMaxIntrinsicWidth].
@@ -1533,8 +1531,7 @@ abstract class RenderBox extends RenderObject {
   /// function couples the child with the parent so that when the child's layout
   /// changes, the parent is notified (via [markNeedsLayout]).
   ///
-  /// Calling this function is expensive and as it can result in O(N^2)
-  /// behavior.
+  /// Calling this function is expensive as it can result in O(N^2) behavior.
   ///
   /// Do not override this method. Instead, implement
   /// [computeMinIntrinsicHeight].
@@ -1610,8 +1607,7 @@ abstract class RenderBox extends RenderObject {
   /// function couples the child with the parent so that when the child's layout
   /// changes, the parent is notified (via [markNeedsLayout]).
   ///
-  /// Calling this function is expensive and as it can result in O(N^2)
-  /// behavior.
+  /// Calling this function is expensive as it can result in O(N^2) behavior.
   ///
   /// Do not override this method. Instead, implement
   /// [computeMaxIntrinsicHeight].