Fix broken GitHub link on Custos website

## Problem

On the Custos website, the “Open on GitHub” link points to:

https://github.com/apache/airavata-custos/tree/develop

That URL is invalid because the repository does not appear to have a `develop` branch.

## Expected behavior

The website should link to the main repository page:

https://github.com/apache/airavata-custos

or to the correct default branch if a branch-specific URL is needed.

## Actual behavior

Clicking “View on Github” opens:

https://github.com/apache/airavata-custos/tree/develop

which results in an invalid GitHub page.

## Suggested fix

Update the website link from:

https://github.com/apache/airavata-custos/tree/develop

to:

https://github.com/apache/airavata-custos

## Note

I will link a seperate Pull Request that fixes this issue.

Search the Custos website source for the invalid /tree/develop GitHub URL used by the “Open on GitHub” or “View on Github” link. Replace it with https://github.com/apache/airavata-custos, then verify that the link opens the repository page.

Written by the indexing model from the issue text.