Fix ruby example for JUnit test

What does this MR do?

This fixes 3 problems:

1. rspec is being executed without bundle exec(it will probably work in CI environment since there is only 1 ruby installation, but it's generally a good idea to use bundle exec)
2. removes specific directory spec/lib which assumes that users always have all tests there. spec/ dir is the default for rspec and I think it's better default in the example
3. output currently is not visible in job because it's being printed only to JUnit file, adding second --format progress fixes that, now it's being printed to both console and JUnit file:

➜  test-artifacts git:(master) ✗ bundle exec rspec --format progress --format RspecJunitFormatter --out rspec.xml
F

Failures:

  1) test describe test example
     Failure/Error: expect(2 + 2).to eq 5
     
       expected: 5
            got: 4
     
       (compared using ==)
     # ./spec/test_spec.rb:7:in `block (2 levels) in <top (required)>'

Finished in 0.01608 seconds (files took 0.13167 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/test_spec.rb:6 # test describe test example

➜  test-artifacts git:(master) ✗ cat rspec.xml 
<?xml version="1.0" encoding="UTF-8"?>
<testsuite name="rspec" tests="1" skipped="0" failures="1" errors="0" time="0.016078" timestamp="2020-04-14T15:00:49+03:00" hostname="Vladimirs-MacBook-Pro.local">
<properties>
<property name="seed" value="53128"/>
</properties>
<testcase classname="spec.test_spec" name="test describe test example" file="./spec/test_spec.rb" time="0.014948"><failure message="
expected: 5
     got: 4

(compared using ==)
" type="RSpec::Expectations::ExpectationNotMetError">Failure/Error: expect(2 + 2).to eq 5

  expected: 5
       got: 4

  (compared using ==)
./spec/test_spec.rb:7:in `block (2 levels) in &lt;top (required)&gt;&apos;</failure></testcase>
</testsuite>

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Does this MR meet the acceptance criteria?

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