[FIX] web: graph: avoid some useless chart renderings

With a slow network, make a new search in the search bar of a graph view
would lead the graph renderer to be rendered twice. This was due to the
fact that in the graph controller template an arrow function is passed
as a prop to the graph renderer. The reactivity system treats that prop
as changing at each graph controller rendering and ask unnecessarily (in
this case) the graph renderer to render.

closes odoo/odoo#121252

Signed-off-by: Géry Debongnie <ged@odoo.com>