style: Align font-family of Calendar block in editor with front-end

[R1shabh-Gupta]

This PR addresses a visual inconsistency in the Twenty Nineteen theme where the Calendar block (.wp-calendar-table) displays a different font-family in the block editor compared to the front-end.

Changes:

• Adds a font-family rule to .wp-calendar-table in style-editor.scss using the existing $font__heading variable and font-family() mixin.
• Ensures consistent typography between front-end and editor.
• Rebuilds style-editor.css and style-editor-rtl.css with the updated styles.

Trac ticket: https://core.trac.wordpress.org/ticket/63331

Before

Before.mov

After

After.mov

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