Fixes #14051: Preserve search term when refreshing contacts

[codewithdipesh]

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Description

The fix is straightforward - I've removed the line in RefreshDirectoryTask.onPostExecute() that was explicitly clearing the search field activity.contactFilterView.clear(), while maintaining the call to reset the query filter. This allows the contacts to refresh properly while preserving the user's search term.

I tested the fix by:
-starting a new chat
-Searching for the contact by name (not found initially)
-Clicking "refresh contacts"
-Verifying the search term remained in the search field
-Confirming the newly added contact appears in the filtered results after refresh

The fix was tested on a Pixel 7 Pro running Android 15 with Signal version 7.38.5

[alex-signal]

Thanks! this was pulled into 7.39