update pori demo link destination

[elewis2]

Copied from comment by @mathieulemieux :

While reviewing pori demo docs, I saw these two links:

• https://github.com/bcgsc/pori/blob/df616ca4f9e1bb30a0807129c5c16e877365692b/docs/demo.md?plain=1#L3
• https://github.com/bcgsc/pori/blob/df616ca4f9e1bb30a0807129c5c16e877365692b/docs/graphkb/index.md?plain=1#L51 from which we are being redirected to the docs on GH and find it a bit confusing. What about removing them or changing them for the /ipr and /graphkb routes?

Originally posted by @mathieulemieux in https://github.com/bcgsc/pori/issues/59#issuecomment-1154473979

[mathieulemieux]

See @creisle reply here: https://github.com/bcgsc/pori/pull/59#issuecomment-1162011080