You're pretty safe, if you want to be really cautious then just avoid touching the CRT while removing the card. The charge in the tube isn't distributed through the logic board or that card, just the analog board and the CRT.
That said i'm pretty sure the Macintosh SE has bleeder circuitry to discharge the tube on shutdown anyway, the last few times I discharged my SE CRT it didn't have any charge in it at all despite the fact it had only been running a few minutes earlier. It must have that circuitry on the analog board or in the flyback transformer (entirely possible, as the flyback is a later revision from the 128k, 512k & Plus, despite the fact the CRTs are the same).