Update Certified CNF Brand Guide pdf

[lixuna]

A new version of the Certified CNF Brand Guide is available to be uploaded to this url: https://github.com/cncf/artwork/blob/master/other/certified-cnf/certified-cnf-brand-guide.pdf

Please remove the placeholder image (comic sans text) and upload the attached pdf.

Thank you for your help!

CNF_Certified_BrandGuide_061322.pdf

[lixuna]

cc @KTan1226 @Charley-Mann @cjyabraham

[thetwopct]

(Housekeeping) Looks like this was done, thanks!