fix(kubernetes/kubectl): add exe to url for windows

[ChipWolf]

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Per #30398, aqua doesn't appear to add .exe to the URL for Windows, this change ensures the correct URL is used for Windows.

[suzuki-shunsuke]

Same.

• fix(kubernetes/kubectl): add exe file extension for windows #30398 (comment)

[suzuki-shunsuke]

• fix(kubernetes/kubectl): add exe file extension for windows #30398 (comment)