Update OpenCost to incubating

[caniszczyk]

cncf/toc#1046

Pre-submission checklist:

Please check each of these after submitting your pull request:

• Are you only including a repo_url if your project is 100% open source? If so, you need to pick the single best GitHub repository for your project, not a GitHub organization.
• Is your project closed source or, if it is open source, does your project have at least 300 GitHub stars?
• Have you picked the single best (existing) category for your project?
• Does it follow the other guidelines from the new entries section?
• Have you added your SVG to hosted_logos and referenced it there?
• Does your logo clearly state the name of the project/product and follow the other guidelines?
• Does your project/product name match the text on the logo?
• Have you verified that the Crunchbase data for your organization is correct (including headquarters and LinkedIn)?

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