replaced bootstrap 2 with bootstrap 3 classes

[cioddi]

No description provided.

[mary-poppins]

Thanks for the PR! Please check the items below to help us merge this faster. See the contributing docs for more information.

• Uses the issue template (#7433)

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Then, update the pull request with git push -f.

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[mary-poppins]

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[mary-poppins]

CLA signature verified! Thank you!

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[IgorMinar]

thanks!