removing an install html file could cause incompatibility with some software (not in this case)
it's not security risk if you are not using the file, MS might have included it as an html so if they updated a term of service or patch the html could link to a page that has that info.
I'm not sure what you perceive the security risk as? do you think having this file on your Mac is like a macro that could cause damage or someone could alter the file to direct you to a compromised website.
instead of deleting it you could .zip the file and leave the archive. In the event that any part of the MS Office suite needs it and cant find it you can unzip it. the zip file would be there but inaccessible until it was unarchived.