hide Dask warnings on the plotting guides (#1423)

Author: maximlt

doc/user_guide/Plotting.ipynb

@@ -2,11 +2,30 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
    "source": [
     "# Plotting"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "tags": [
+     "hide-cell"
+    ]
+   },
+   "outputs": [],
+   "source": [
+    "# Cell hidden on the website (hide-cell in tags)\n",
+    "# https://github.com/holoviz/holoviews/pull/6391\n",
+    "import warnings\n",
+    "\n",
+    "warnings.filterwarnings(\"ignore\", message=\"When grouping with a length-1 list-like\", category=FutureWarning)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

doc/user_guide/Plotting_with_Matplotlib.ipynb

@@ -2,14 +2,35 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
    "source": [
     "# Plotting with Matplotlib"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "tags": [
+     "hide-cell"
+    ]
+   },
+   "outputs": [],
+   "source": [
+    "# Cell hidden on the website (hide-cell in tags)\n",
+    "# https://github.com/holoviz/holoviews/pull/6391\n",
+    "import warnings\n",
+    "\n",
+    "warnings.filterwarnings(\"ignore\", message=\"When grouping with a length-1 list-like\", category=FutureWarning)"
+   ]
+  },
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
    "source": [
     "This page demonstrates the use of the **Matplotlib** plotting backend, the equivalent page demonstrating the Plotly backend may be found [here](Plotting_with_Plotly.ipynb)\n",
     "\n",

doc/user_guide/Plotting_with_Plotly.ipynb

@@ -2,14 +2,35 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
    "source": [
     "# Plotting with Plotly"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "tags": [
+     "hide-cell"
+    ]
+   },
+   "outputs": [],
+   "source": [
+    "# Cell hidden on the website (hide-cell in tags)\n",
+    "# https://github.com/holoviz/holoviews/pull/6391\n",
+    "import warnings\n",
+    "\n",
+    "warnings.filterwarnings(\"ignore\", message=\"When grouping with a length-1 list-like\", category=FutureWarning)"
+   ]
+  },
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
    "source": [
     "This page demonstrates the use of the **Plotly** plotting backend, the equivalent page demonstrating the Matplotlib backend may be found [here](Plotting_with_Matplotlib.ipynb)\n",
     "\n",