Small typo (#345)

Author: seanccho

examples/optimizers_lazyadam.ipynb

@@ -90,7 +90,7 @@
       "source": [
         "# LazyAdam\n",
         "\n",
-        "> LazyAdam is a variant of the Adam optimizer that handles sparse updates moreefficiently.\n",
+        "> LazyAdam is a variant of the Adam optimizer that handles sparse updates more efficiently.\n",
         "    The original Adam algorithm maintains two moving-average accumulators for\n",
         "    each trainable variable; the accumulators are updated at every step.\n",
         "    This class provides lazier handling of gradient updates for sparse\n",