timeline icons: use codicon registry for now

src/vs/workbench/contrib/timeline/browser/timeline.contribution.ts

@@ -18,8 +18,7 @@ import { MenuId, MenuRegistry } from 'vs/platform/actions/common/actions';
 import { ICommandHandler, CommandsRegistry } from 'vs/platform/commands/common/commands';
 import { ExplorerFolderContext } from 'vs/workbench/contrib/files/common/files';
 import { ResourceContextKey } from 'vs/workbench/common/resources';
-import { Codicon } from 'vs/base/common/codicons';
-import { registerIcon } from 'vs/platform/theme/common/iconRegistry';
+import { Codicon, registerIcon } from 'vs/base/common/codicons';
 
 
 const timelineViewIcon = registerIcon('timeline-view-icon', Codicon.history, localize('timelineViewIcon', 'View icon of the timeline view.'));