Content: Update "Retro Funding + Rounds" contents based on legal requirement

[shaunop]

Legal has advised that we should not combine the terms "Retro Funding" with "Round". So, we need to update the following:

Application title

Old: "Apply for Retro Funding Round 5: OP Stack" New: "Apply for Retro Funding 5: OP Stack" (remove the word Round)

Callouts

Old: "Now taking applications for Retro Funding Round 5: OP Stack" New: "Now taking applications for Retro Funding 5: OP Stack" (remove the word Round)

Old: "You applied to Retro Funding Round 5: OP Stack" New: "You applied to Retro Funding 5: OP Stack"

[sbvhev]

@shaunop Ready to review