Update to remove 768px breakpoint

Author: gustavo-olmedo

dotcom-rendering/src/layouts/PuzzlesLayout.test.tsx

@@ -79,7 +79,6 @@ describe('PuzzlesLayout', () => {
 			[1140, 'header-leftcol-1280px', 1280],
 			[980, 'header-desktop-1024px', 1024],
 			[768, 'header-tablet-979px', 979],
-			[740, 'header-tablet-768px', 768],
 			[660, 'header-mobile-phablet-669px', 669],
 			[480, 'header-mobile-landscape-480px', 480],
 			[375, 'header-mobile-medium-393px', 393],

dotcom-rendering/src/layouts/PuzzlesLayout.tsx

@@ -75,7 +75,6 @@ const headerSources = [
 	{ breakpoint: breakpoints.wide, filename: 'header-wide-1440px' },
 	{ breakpoint: breakpoints.leftCol, filename: 'header-leftcol-1280px' },
 	{ breakpoint: breakpoints.desktop, filename: 'header-desktop-1024px' },
-	{ breakpoint: 768, filename: 'header-tablet-979px' },
 	{ breakpoint: breakpoints.tablet, filename: 'header-tablet-768px' },
 	{
 		breakpoint: breakpoints.phablet,