Revert "Merge branch 'reafactor-validate-type-property' into 'main'"

What does this MR do?

revert(GlChartSeriesLabel): Add validation for type prop

This reverts !2714 (merged), which caused failures downstream in GitLab.

This also highlights that we have missing test coverage in GitLab UI.

It turns out that GlChartLegend passes the series's type (e.g., "bar") to GlChartSeriesLabel, while GlChartSeriesLabel expects only "solid" or "dashed".

It's not immediately clear what the correct fix is, hence this revert.

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
• [-] If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• [-] If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• If the MR changes a component's API, integration MR(s) have been opened in the following projects to ensure that the @gitlab/ui package can be upgraded quickly after the changes are released:
  • GitLab: mr_url
  • CustomersDot: mr_url
  • Status Page: mr_url
• Added the ~"component:*" label(s) if applicable.