Fix documentation for getInsertedId(s) methods on insert results

Per PHPLIB-93, these classes should always have an ID, regardless of whether the driver needed to generate one.

src/InsertManyResult.php

@@ -38,7 +38,7 @@ class InsertManyResult
     }
 
     /**
-     * Return the map of inserted IDs that were generated by the driver.
+     * Return a map of the inserted documents' IDs.
      *
      * The index of each ID in the map corresponds to the document's position
      * in bulk operation. If the document already an ID prior to insertion (i.e.

src/InsertOneResult.php

@@ -38,7 +38,7 @@ class InsertOneResult
     }
 
     /**
-     * Return the inserted ID that was generated by the driver.
+     * Return the inserted document's ID.
      *
      * If the document already an ID prior to insertion (i.e. the driver did not
      * need to generate an ID), this will contain its "_id". Any