bind:clientWidth shows up in SSR

[Rich-Harris]

it shouldn't

[Conduitry]

Probably none of the read-only bindings should be written out in SSR. This includes the four dimension bindings (offset/client width/height), but also a few of the media bindings and maybe some others. There's an is_readonly value that's calculated for each binding, but only for the DOM renderer. Perhaps this should be moved to the common (unwrapped) Binding AST class so that the SSR renderer can also make use of it and skip them when appropriate.