Payment page is shown in header

[shivaenigma]

In the navigation header, this page is unnecessarily showing up. Non bitcoin custom may click on this page and it shows empty is thus a UI nuisance. Things about how:

• We can maybe remove the page from navigation header
• Hide the page publicly and only show when during bitcoin checkout
• Alternatively a simple solution for now is to show something meaningful when user clicks on the page like
  This is a placeholder page for Bitcoin Payment. Please ignore this page

[ashthecoder05]

This is fixed in non block theme. For block theme, we need to think of a different solution. I'll verify on block theme and update the task

[shivaenigma]

Closing. Addressed in #343