Fix 'perceptron-part-2' references in tracks

Author: loic-brtd

content/tracks/main-tracks/the-nature-of-code-2/index.json

@@ -112,7 +112,7 @@
       "title": "Neural Networks",
       "videos": [
         "neural-networks/2-perceptron-part-1",
-        "neural-networks/3-perceptron-part 2",
+        "neural-networks/3-perceptron-part-2",
         "neural-networks/4-multilayer-perceptron-part-1",
         "neural-networks/5-multilayer-perceptron-part-2",
         "challenges/92-xor-problem"

content/tracks/side-tracks/neural-networks/index.json

@@ -4,7 +4,7 @@
   "videos": [
     "neural-networks/1-introduction",
     "neural-networks/2-perceptron-part-1",
-    "neural-networks/3-perceptron-part 2",
+    "neural-networks/3-perceptron-part-2",
     "neural-networks/4-multilayer-perceptron-part-1",
     "neural-networks/5-multilayer-perceptron-part-2",
     "neural-networks/6-matrix-math-basics",