Fix typo in context menu item

It should be "Share", and not "Shared" as it was specified in some
variants of the English language.

Bug: 424014487
Flag: EXEMPT fixing existing typo
Test: atest DocumentsUIGoogleTests:com.android.documentsui.ContextMenuUiTest
Change-Id: Ife8dc8fd3ba40d75dab0fb2adfa0c68936f56180