fix(deps): update dependency bootstrap to v4.3.1 [security]

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
bootstrap	dependencies	minor	4.2.1 -> 4.3.1	homepage, source

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Release Notes

twbs/bootstrap

### [`v4.3.1`](https://togithub.com/twbs/bootstrap/releases/v4.3.1) [Compare Source](https://togithub.com/twbs/bootstrap/compare/v4.2.1...v4.3.1) - **Security:** Fixed an XSS vulnerability (CVE-2019-8331) in our tooltip and popover plugins by implementing a new HTML sanitizer - Fixed a small issue with our RFS (responsive font sizes) mixins

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