Change example text in variables.go

Instead of 'short', which is a common programming language keyword, use something random like 'apple'. This way it prevents confusion from people learning explicit variable declaration, and thinking the type is a short instead of a string.

examples/variables/variables.go

@@ -28,7 +28,7 @@ func main() {
 
     // The `:=` syntax is shorthand for declaring and
     // initializing a variable, e.g. for
-    // `var f string = "short"` in this case.
+    // `var f string = "apple"` in this case.
-    f := "short"
+    f := "apple"
     fmt.Println(f)
 }