Tutorial validation: use `-B` when doing a diff between expected/actual output

[ybyzek]

See #579 for more context.

When I build the window-final-result tutorial locally, it appears to succeed locally but ultimately fails because the diff isn't exactly -- there are blank lines:

cat tutorial-steps/dev/expected-count.txt
5
1
1
2

versus

cat tutorial-steps/dev/outputs/actual-count.txt
5
1
1
2

So this check fails:

[16:10:12] ~/git/kafka-tutorials/_includes/tutorials/window-final-result/kstreams/code(GH-461) ✗: bash -c 'diff --strip-trailing-cr <(cat tutorial-steps/dev/expected-count.txt) <(cat tutorial-steps/dev/outputs/actual-count.txt)'

4a5,7
> 
> 
> 
[16:10:20] ~/git/kafka-tutorials/_includes/tutorials/window-final-result/kstreams/code(GH-461) ✗: echo $?
1

But this check passes (Notice the addition of the -B flag):

[16:10:22] ~/git/kafka-tutorials/_includes/tutorials/window-final-result/kstreams/code(GH-461) ✗: bash -c 'diff -B --strip-trailing-cr <(cat tutorial-steps/dev/expected-count.txt) <(cat tutorial-steps/dev/outputs/actual-count.txt)'                   

[16:10:35] ~/git/kafka-tutorials/_includes/tutorials/window-final-result/kstreams/code(GH-461) ✗: echo $?
0