fix(SelectDialog): adjust heading level to `h1` #21265

Job	Run time
check-bundle-size	4m 16s
Install Dependencies	1m 19s
reuse-compliance	9s
lint	2m 3s
Build (19)	2m 31s
Build (18)	1m 57s
test / Cypress (base, 18)	3m 20s
test / Cypress (cypress-commands, 19)	2m 8s
test / Cypress (charts, 19)	4m 11s
test / Cypress (main/src/internal, 19)	2m 24s
test / Cypress (main/src/internal, 18)	2m 43s
test / Cypress (main/src/components, 19)	7m 2s
test / Cypress (compat, 19)	2m 7s
test / Cypress (compat, 18)	2m 50s
test / Cypress (cypress-commands, 18)	2m 36s
test / Cypress (charts, 18)	4m 36s
test / Cypress (main/src/components, 18)	7m 35s
test / Cypress (base, 19)	2m 41s
deploy-next-docs	3m 2s
test / Combine Coverage	5s
	59m 35s

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