Use place-hold.it instead of plaecehold.it to create image placeholders (#6320)

Author: echarles

tools/tests/Confined Output.ipynb

@@ -13,11 +13,11 @@
    "source": [
     "markdown image:\n",
     "\n",
-    "<img src=\"http://placehold.it/800x200.png\">\n",
+    "<img src=\"http://place-hold.it/800x200.png\">\n",
     "\n",
     "unconfined markdown image:\n",
     "\n",
-    "<img src=\"http://placehold.it/800x200.png\" class=\"unconfined\">"
+    "<img src=\"http://place-hold.it/800x200.png\" class=\"unconfined\">"
    ]
   },
   {
@@ -48,7 +48,7 @@
     {
      "data": {
       "text/html": [
-       "<img src=\"http://placehold.it/800x200.png\"   />"
+       "<img src=\"http://place-hold.it/800x200.png\"   />"
       ],
       "text/plain": [
        "<IPython.core.display.Image object>"
@@ -60,7 +60,7 @@
     }
    ],
    "source": [
-    "Image(url=\"http://placehold.it/800x200.png\", embed=False)"
+    "Image(url=\"http://place-hold.it/800x200.png\", embed=False)"
    ]
   },
   {
@@ -90,7 +90,7 @@
     }
    ],
    "source": [
-    "Image(url=\"http://placehold.it/800x200.png\", embed=True)"
+    "Image(url=\"http://place-hold.it/800x200.png\", embed=True)"
    ]
   },
   {
@@ -124,7 +124,7 @@
     }
    ],
    "source": [
-    "Image(url=\"http://placehold.it/800x200.png\", embed=True, unconfined=True)"
+    "Image(url=\"http://place-hold.it/800x200.png\", embed=True, unconfined=True)"
    ]
   },
   {
@@ -159,7 +159,7 @@
     }
    ],
    "source": [
-    "Image(url=\"http://placehold.it/1800x200.jpg\", embed=True, retina=True)"
+    "Image(url=\"http://place-hold.it/1800x200.jpg\", embed=True, retina=True)"
    ]
   },
   {