examples: Drop figshare embedding and use gist

Author: georgebisbas

examples/mpi/overview.ipynb

@@ -832,12 +832,12 @@
     "The Devito compiler applies several optimizations before generating code.\n",
     "\n",
     "* Redundant halo exchanges are identified and removed. A halo exchange is redundant if a prior halo exchange carries out the same `Function` update and the data is not “dirty” yet.\n",
-    "* Halo exchange communications that could be ``fired\" together are preferred over being scattered all over the code.\n",
+    "* Halo exchange communications that could be fired together are preferred over being scattered all over the code.\n",
     "* Halo exchanges could also be reshuffled to maximize the extension of the computation/communication overlap region.\n",
     "\n",
     "## Computation/communication patterns\n",
     "\n",
-    "<iframe src=\"https://widgets.figshare.com/articles/27890487/embed?show_title=1\" width=\"732\" height=\"368\" allowfullscreen frameborder=\"0\"></iframe>\n",
+    "![mpi-modes](https://gist.githubusercontent.com/georgebisbas/aa0e6a2f658728f1bb360f328ee6984a/raw/8c625fb2216dc6f67035856e63985516bbdeb340/mpi-modes.drawio.svg)\n",
     "\n",
     "Additionally, the Devito compiler offers a few modes of different computation and communication strategies, each exhibiting superiority under specific conditions for a kernel, such as operational intensity, memory footprint, the number of utilized ranks, and the characteristics of the cluster’s interconnect. Some of the best patterns are namely `basic`, `diagonal`, and `full`. Those have proven to be effective in improving the efficiency and scalability of computations, under several scnarios.\n",
     "\n",