fix(bootstrap): headings font-families don't provide fallback values #5097

Job	Run time
Status check > Unit	1s
CI \| Unit	1s
CI \| Visual	1s
Compile themes / run	51s
Render test pages / verify	8s
Lint scripts / run	44s
Lint styles / run (default)	1m 26s
Lint styles / run (bootstrap)	1m 23s
Lint styles / run (material)	1m 26s
Lint styles / run (classic)	1m 29s
Lint styles / run (fluent)	1m 6s
Render test pages / run	0s
Status check > Lint scripts	1s
Status check > A11y / prepare	1s
Create screenshots / run (default)	2m 18s
Create screenshots / run (bootstrap)	2m 56s
Create screenshots / run (material)	2m 14s
Create screenshots / run (classic)	2m 10s
Create screenshots / run (fluent)	2m 19s
Status check > A11y / run-checks (1)	2m 28s
Status check > A11y / run-checks (2)	2m 35s
Status check > A11y / run-checks (3)	2m 28s
Status check > A11y / run-checks (4)	2m 39s
Status check > Lint styles	1s
Detect changes	12s
Status check > Visual	1s
	30m 59s

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