fix: Make sure the enumerable is a List

[sandercox]

This allows to setup the Tags field which is a List. IEnumerable of the SelectListIterator does not convert to a List. An IEnumerable of List does.

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After PR#373 the code was introduced to Trim installer URLs, and trim these properties.

Apparently this works for these URLs that get set to a property of IEnumerable<string> but when trying to set the Tags when setting optional default locale fields, this threw an Exception:

System.ArgumentException: 'Object of type 'System.Linq.Enumerable+SelectListIterator`2[System.String,System.String]' cannot be converted to type 'System.Collections.Generic.List`1[System.String]'.'

Apparently an IEnumerable<string> can be set to a List<string> when the enumerable comes from an actual List<string> but not from a Linq based List.

Turning the Trimmed list back into a real List (it originates from Prompt.List()) it seems to work for both URLs and the Tags.

Microsoft Reviewers: codeflow:open?pullrequest=https://github.com/microsoft/winget-create/pull/390&drop=dogfoodAlpha

[ryfu-msft]

/azp run

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[ryfu-msft]

/azp run

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