Fix redirect when using lowercase reponame (#18775)
Fix redirect when using lowercase reponame (#18775)

* Previously,  `GET {username}/{reponame}/raw///file-path` (the middle two slashes are blank to get the default branch) when the repo name has uppercase letters, e.g., https://try.gitea.io/AbdulrhmnGhanem/CH330_Hardware, using a lowercase version of the name redirected to the correct URL
* In other words both
   * `GET https://try.gitea.io/AbdulrhmnGhanem/CH330_Hardware/raw///images/back.png`
   * `GET https://try.gitea.io/AbdulrhmnGhanem/ch330_hardware/raw///images/back.png`
were redirecting to ` GET https://try.gitea.io/AbdulrhmnGhanem/CH330_Hardware/raw/branch/master/images/back.png`
This isn't the case after  #17551. Specifically because of this [line](https://github.com/zeripath/gitea/blob/cbd5eecd148dfca5fcb1a3da469e491a84f6b32b/modules/context/repo.go#L860).
go-gitea/gitea,go-gitea/gitea,go-gitea/gitea