[SN-120] Added a note around url expiring after 30 days of the export being created. (#1428)

Author: ovalle15

examples/exports/composite_mask_export.ipynb

@@ -96,6 +96,7 @@
       "metadata": {},
       "source": [
         "#### Composite masks\n",
+        "**IMPORTANT :** The URL for the ```composite_mask``` from exports older than 30 days will no longer be accessible. To obtain a functional URL after this period, please generate a new export for the mask.\n",
         "1. A single mask url contains all mask instances from a single label. For videos a composite mask contains all mask instances for the frame in each label. \n",
         "2. The export and mask URL adhere to the following convention:\n",
         "  - ***Image example***\n",
@@ -165,7 +166,7 @@
     {
       "metadata": {},
       "source": [
-        "Here's an example of an entry featuring a composite mask containing the mask instance's RGB color uniquely associated with the annotation.\n",
+        "Here's an example of an entry featuring a composite mask (see image above) containing the mask instance's RGB color uniquely associated with the annotation.\n",
         "\n",
         "```json\n",
         "    {\n",