Update install.md

(cherry picked from commit 0ff9c32)

Author: ospillinger

docs/cluster/install.md

@@ -42,7 +42,7 @@ cortex get classifier
 
 # Classify a sample
 curl -X POST -H "Content-Type: application/json" \
-     -d '{ "sepal_length": 5.2, "sepal_width": 3.6, "petal_length": 1.4 "petal_width": 0.3 }' \
+     -d '{ "sepal_length": 5.2, "sepal_width": 3.6, "petal_length": 1.4, "petal_width": 0.3 }' \
      <API endpoint>
 ```