Wrong color on description text on components

### Description of the bug

Some users have said that our description text have low contrast. While looking into this I found out that Apps and the design system used different colors for the descriptions. We should change to the one from the DS which is a little darker. It seems to come from the Altinn Tokens file. How we fix this is up to the developers, but we either need to switch over to the design system tokens file or change the color in the Altinn file.


- [ ] Change `semantic/text/neutral/subtle` from `#68707C`to `#4B5563`

## Accessibility
We are not breaching any WCAG guidelines with the color we are using today, it has good enough contrast. But we should listen to the users feedback and make it a little darker.

### Steps To Reproduce

Test color value on an app with a description

### Additional Information

_No response_

Start by locating the Altinn Tokens file and the definition of semantic/text/neutral/subtle used by component descriptions. Compare it with the design system token value, update the source so the token is #4B5563, and verify an app description renders with the darker color.

Written by the indexing model from the issue text.