firefox78: Update to 78.8.0

Security Vulnerabilities fixed in Firefox ESR 78.8

#CVE-2021-23969: Content Security Policy violation report could have
contained the destination of a redirect

#CVE-2021-23968: Content Security Policy violation report could have
contained the destination of a redirect

#CVE-2021-23973: MediaError message property could have leaked
information about cross-origin resources

#CVE-2021-23978: Memory safety bugs fixed in Firefox 86 and Firefox ESR
78.8

(nia)