shell: Drop already bundled nav.css
shell: Drop already bundled nav.css

webpack builds shell.scss, which in turn imports nav.scss.
So, the requirement 'shell/index.css' is enough.

Fixes #15057

Signed-off-by: Stanislav Levin <d8f28bdabcfedd2870feddb04c5f1bca6a417bec@altlinux.org>
deryni/cockpit,deryni/cockpit,deryni/cockpit,mvollmer/cockpit,garrett/cockpit,garrett/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,garrett/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,martinpitt/cockpit,deryni/cockpit,cockpit-project/cockpit,mvollmer/cockpit