projects.html: Fix close sign on filter dialog box

[pra17dod]

This fixes the close position which was out of the filter box and changes 'Filter Projects' heading tag: h6 to h4 Fixes #785

Preview of dialog box

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[pra17dod]

@abhishalya @anshalshukla @CLiu13 Please review the PR.

[pra17dod]

@abhishalya Please Review the PR