add translation context for "saved" (#8982)

src/view/shell/Drawer.tsx

···
           <Bookmark style={[t.atoms.text]} width={iconWidth} />
         )
       }
-      label={_(msg`Saved`)}
+      label={_(msg({message: 'Saved', context: 'link to bookmarks screen'}))}
       onPress={onPress}
     />
   )

src/view/shell/desktop/LeftNav.tsx

···
                 width={NAV_ICON_WIDTH}
               />
             }
-            label={_(msg`Saved`)}
+            label={_(
+              msg({
+                message: 'Saved',
+                context: 'link to bookmarks screen',
+              }),
+            )}
           />
           <NavItem
             href={currentAccount ? makeProfileLink(currentAccount) : '/'}