[Fix]: Dropdown selected item parsing

[riitasointi]

Description

PR removes problematic code which tried to parse only the children text content of a selected <DropdownItem> into the Dropdown button element.

This logic created problems with elements like <FormattedMessage /> (from react-intl) and patterns like this

const Foo = () => 'This text will not show up in button when selected'
...
<DropdownItem>
   <Foo />
</DropdownItem>

PR also raises version to 10.0.3 for a hotfix release

Motivation and Context

This bug was reported by a user and severely affects their application

How Has This Been Tested?

Styleguidist, CRA with react-intl <FormattedMessage />

Screenshots (if appropriate):

☝️ Initial bug report image

Release notes

Dropdown

• Fix a bug where selected item text did not correctly appear in Dropdown button

[jenkrisu]

Tested also in Styleguidist with NVDA (Firefox, Edge, Chrome). ✔️