Remove the opacity from process upcoming/past/all filters for accessible contrast

[ahukkanen]

🎩 What? Why?

The color contrast between the body background and the time filters for proposals is not sufficient.

This removes the opacity to make the contrast ratio sufficient.

The background color is #fafafa and the foreground color is #b6b2b5 (= #726a70 with 50% opacity against the background).

📌 Related Issues

• Related to Seek alternatives to design changes due to accessibility #5942, Accessibility/final #6246, Improve accessibility vol 2 #6124, Improve accessibility issues #5684

Testing

1. Go to: https://webaim.org/resources/contrastchecker/
2. Add the old foreground color (#b6b2b5) as the foreground color
3. Add the body background color (#fafafa) as the background color
4. See the contrast ratio
5. Repeat the test with the updated foreground color (#726a70)

📋 Checklist

• ❓ CONSIDER adding a unit test if your PR resolves an issue.
• ✔️ DO check open PR's to avoid duplicates.
• ✔️ DO keep pull requests small so they can be easily reviewed.
• ✔️ DO build locally before pushing.
• ✔️ DO make sure tests pass.
• ✔️ DO make sure any new changes are documented in docs/.
• ✔️ DO add and modify seeds if necessary.
• ✔️ DO add CHANGELOG upgrade notes if required.
• ✔️ DO add to GraphQL API if there are new public fields.
• ✔️ DO add link to MetaDecidim if it's a new feature.
• ❌AVOID breaking the continuous integration build.
• ❌AVOID making significant changes to the overall architecture.

📷 Screenshots

Before:

After: