Support Forums: Standardize loader and constructor style

[dd32]

Follow-up to #677 / https://meta.trac.wordpress.org/ticket/2214.

This standardizes the support-forums loader and no-argument component instantiations so the active PHPCS rules pass without local suppressions:

• converts support-forums loader includes from parenthesized include calls to include statements
• converts support-forums no-argument component instantiations from bare new Foo to new Foo()

No behavior changes intended.

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Props dd32.

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