add colour picker unit tests (#13363)

* a11y improvements

* tweak

* tests

* add changeset

* add changeset

* pass new value to change

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Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>

Author: hannahblair

.changeset/plain-beans-roll.md

@@ -0,0 +1,6 @@
+---
+"@gradio/colorpicker": patch
+"gradio": patch
+---
+
+fix:add colour picker unit tests