Update kdiff3 to 1.8.4

Summary:

• Fix compare over network with KIO
• Fix typos in man page

Test Plan: Merge two conflicting git branches made on purpose.

Reviewers: Triage Team, JoshStrobl

Reviewed By: Triage Team, JoshStrobl

Subscribers: JoshStrobl

Differential Revision: https://dev.getsol.us/D9585