Fix issue467- Use the imperative form for the bullet list

[sbvkrishna]

Fixes issue #467
Use the Imperative form for the bullet list on the Continuous Integration page ( in buildbots.rst file )

[the-knights-who-say-ni]

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[hugovk]

References:

• https://www.merriam-webster.com/dictionary/checkout
• https://www.dictionary.com/browse/check--out
• https://www.oxfordlearnersdictionaries.com/definition/english/checkout
• http://notaverb.com/checkout
• https://grammarist.com/spelling/checkout-check-out/
• https://www.grammarphobia.com/blog/2019/05/checkout.html

[willingc]

Thanks @sbvkrishna for the documentation grammar change.