Clean up date format code in docs (#1299)

CONTRIBUTING.md

@@ -423,15 +423,16 @@ will be cached.
 
       ```kotlin
       private fun parseDate(dateStr: String): Long {
-          return runCatching { DATE_FORMATTER.parse(dateStr)?.time }
-              .getOrNull() ?: 0L
+          return try {
+              dateFormat.parse(dateStr)!!.time
+          } catch (_: ParseException) {
+              0L
+          }
       }
 
-      companion object {
-          private val DATE_FORMATTER by lazy {
+      private val dateFormat by lazy {
           SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.ENGLISH)
       }
-      }
       ```
 
       Make sure you make the `SimpleDateFormat` a class constant or variable so it doesn't get