fixup link to intro tutorial on tutorials page

closes #219

notebooks/4.2-paho-mqtt-colab-sdl-demo-test.ipynb

@@ -30,12 +30,7 @@
         "</p>\n",
         "\n",
         "<p align=\"center\">\n",
-        "<sup>\n",
-        "\n",
-        "[https://www.calsoft.com/what-is-industry-4-0/](https://www.calsoft.com/what-is-industry-4-0/)\n",
-        "https://www.calsoft.com/what-is-industry-4-0/\n",
-        "\n",
-        "</sup>\n",
+        "<sup><a href=\"https://www.calsoft.com/what-is-industry-4-0/\">https://www.calsoft.com/what-is-industry-4-0/</a></sup>\n",
         "</p>\n",
         "\n",
         "While Industry 4.0 is accelerating the efficiency with which manufacturers develop\n",

notebooks/README.md

@@ -3,7 +3,7 @@
 This is a collection of tutorial notebooks and demonstrations for the
 self-driving-lab-demo! First, you should get started with the main, public-facing tutorial. Just click
 the following "Open in Colab" badge: [![Open In
-Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/sparks-baird/self-driving-lab-demo/blob/main/notebooks/4.1-paho-mqtt-colab-sdl-demo-search.ipynb)
+Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/sparks-baird/self-driving-lab-demo/blob/main/notebooks/4.2-paho-mqtt-colab-sdl-demo-test.ipynb)
 
 <!-- Next comes the use of the PicoW-SDL-Demo via hosting a local web server (`Pico W / MicroPython implementation`) and
 then using Internet-of-things-style communication to remotely control the PicoW