Fixed cell toolbar select font size

IPython/html/static/notebook/less/celltoolbar.less

@@ -38,6 +38,10 b''
     padding-top: 3px;
 }
 
+.celltoolbar select {
+    font-size: 87%;
+}
+
 .celltoolbar label {
     margin-left: 5px;
     margin-right: 5px;