RN iOS: Share extension channels search box should always be visible

Description

Repro:
1. Find a file from camera or file system and share to Mattermost
2. Click on "channels"
3. Swipe up the channel list

Observed:

QA Test Steps

None

Status

Mana

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Assignee

Unassigned

QA Assignee

None

Reporter

Shota Gvinepadze

Epic Link

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Fix versions

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Mattermost Team

Unassigned

Sprint

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Labels

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QA Testing Areas

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GitHub Issue

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Components

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