Broken icon image for Google OAuth2 provider

[kvaster]

Gitea Version

1.16.0

Git Version

No response

Operating System

No response

How are you running Gitea?

Built myself from v1.16.0 tag using golang 1.17.6

Database

No response

Can you reproduce the bug on the Gitea demo site?

No

Log Gist

No response

Description

Google image icon is broken after this PR: #16544

Google provider's name is 'gplus' traditionally and SimpleProvider creates icon image url using name. But no gplus.png is available - only google.png is available.

Screenshots