Fix type checking for IHttpClientHandlerProvider in Eureka client

[TimHess]

Description

Brings #1141 to the 4.x line

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[hananiel]

/azp run cleanup-code

[azure-pipelines]

No commit pushedDate could be found for PR 1146 in repo SteeltoeOSS/Steeltoe

[bart-vmware]

No commit pushedDate could be found for PR 1146 in repo SteeltoeOSS/Steeltoe

See microsoft/winget-pkgs#111634 (comment):