Fix links of docs on the comment (facebook#12795)

Author: Ende93

packages/react/src/ReactChildren.js

@@ -264,7 +264,7 @@ function forEachSingleChild(bookKeeping, child, name) {
 /**
  * Iterates through children that are typically specified as `props.children`.
  *
- * See https://reactjs.org/docs/react-api.html#react.children.foreach
+ * See https://reactjs.org/docs/react-api.html#reactchildrenforeach
  *
  * The provided forEachFunc(child, index) will be called for each
  * leaf child.
@@ -333,7 +333,7 @@ function mapIntoWithKeyPrefixInternal(children, array, prefix, func, context) {
 /**
  * Maps children that are typically specified as `props.children`.
  *
- * See https://reactjs.org/docs/react-api.html#react.children.map
+ * See https://reactjs.org/docs/react-api.html#reactchildrenmap
  *
  * The provided mapFunction(child, key, index) will be called for each
  * leaf child.
@@ -356,7 +356,7 @@ function mapChildren(children, func, context) {
  * Count the number of children that are typically specified as
  * `props.children`.
  *
- * See https://reactjs.org/docs/react-api.html#react.children.count
+ * See https://reactjs.org/docs/react-api.html#reactchildrencount
  *
  * @param {?*} children Children tree container.
  * @return {number} The number of children.
@@ -369,7 +369,7 @@ function countChildren(children) {
  * Flatten a children object (typically specified as `props.children`) and
  * return an array with appropriately re-keyed children.
  *
- * See https://reactjs.org/docs/react-api.html#react.children.toarray
+ * See https://reactjs.org/docs/react-api.html#reactchildrentoarray
  */
 function toArray(children) {
   const result = [];
@@ -386,7 +386,7 @@ function toArray(children) {
  * Returns the first child in a collection of children and verifies that there
  * is only one child in the collection.
  *
- * See https://reactjs.org/docs/react-api.html#react.children.only
+ * See https://reactjs.org/docs/react-api.html#reactchildrenonly
  *
  * The current implementation of this function assumes that a single child gets
  * passed without a wrapper, but the purpose of this helper function is to