Rename AccessibilityGestureNavigationTutorial to AccessibilityShortcutsTutorial

AccessibilityGestureNavigationTutorial is not only for displaying
tutorial for accessibility gesture shortcut. It's used for display the
tutorials for all the selected accessibility shortcuts. Renamed the
class to match it's responsibility.

Bug: N/A
Flag: EXEMPT Strict mechanical refactors
Test: build succeed locally

Change-Id: I1dd212abc660454e77f18f770c2ecc17be320eaa