(fix) Consistently style multi-select field labels

[samuelmale]

Requirements

• This PR has a title that briefly describes the work done including the ticket number. If there is a ticket, make sure your PR title includes a conventional commit label. See existing PR titles for inspiration.
• My work conforms to the OpenMRS 3.0 Styleguide and design documentation.
• My work includes tests or is validated by existing tests.

Summary

This PR aims at fixing a few minor issues related to #232. It basically:

1. Ensures that a required field's label is highlighted using an asterisk
2. Ensures that the field label is styled conventionally

Screenshots

Before:

After:

Related Issue

Other

[github-actions]

Size Change: +81 B (+0.01%)

Total Size: 1.04 MB

ℹ️ View Unchanged

Filename	Size	Change
dist/184.js	11.2 kB	0 B
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dist/300.js	706 B	0 B
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dist/335.js	955 B	0 B
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dist/465.js	181 kB	0 B
dist/540.js	2.64 kB	0 B
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dist/635.js	14.3 kB	0 B
dist/708.js	245 kB	+40 B (+0.02%)
dist/8.js	3.67 kB	0 B
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dist/99.js	690 B	0 B
dist/993.js	3.08 kB	0 B
dist/998.js	15.5 kB	0 B
dist/main.js	300 kB	+41 B (+0.01%)
dist/openmrs-form-engine-lib.js	3.75 kB	0 B

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[denniskigen]

LGTM. Thanks, @samuelmale!