Update test to use String.prototype.substring() over .substr()

 * `String.prototype.substr()` was deprecated, so the test is
      updated to use `String.prototype.substring()` instead

exercises/practice/robot-name/robot-name.test.ts

@@ -1,10 +1,10 @@
 import { Robot } from './robot-name'
 
 const areSequential = (name1: string, name2: string): boolean => {
-  const alpha1 = name1.substr(0, 2)
-  const alpha2 = name2.substr(0, 2)
-  const num1 = Number(name1.substr(2, 3))
-  const num2 = Number(name2.substr(2, 3))
+  const alpha1 = name1.substring(0, 2)
+  const alpha2 = name2.substring(0, 2)
+  const num1 = Number(name1.substring(2, 5))
+  const num2 = Number(name2.substring(2, 5))
 
   const numDiff = num2 - num1
   const alphaDiff =