fix(dropdown): styles for slotted menu

[bennypowers]

What I did

1. apply dropdown menu styles to slotted menu

Testing Instructions

1. try the versions dropdown on the dp https://deploy-preview-2713--patternfly-elements.netlify.app/components

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: a5cbfe5018bca8a15d882450275af2ca78b5cb59

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[netlify[bot]]

✅ Deploy Preview for patternfly-elements ready!

Name	Link
🔨 Latest commit	8c9030fb3903e5ae103d780f510fbdcc4afc952b
😎 Deploy Preview	https://deploy-preview-2713--patternfly-elements.netlify.app/

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