codemirror: do not set too high z-index for maximize, this have to remain lower than hint popup

bt5/erp5_code_mirror/SkinTemplateItem/portal_skins/erp5_code_mirror/code_mirror_support.xml

@@ -125,7 +125,7 @@
    bottom: 0;\n
    top: 0 !important;\n
    left: 0 !important;\n
-   z-index: 4242 !important;\n
+   z-index: 2 !important;\n
    overflow: hidden !important;\n
  }\n
 \n