Update refresh_tokens.rst (#4528)
Update refresh_tokens.rst (#4528)

The doc has a different value for RefreshTokenUsage enum.
Old value: RefreshTokenUsage.OneTime
Value that I have in the latest version on my machine: RefreshTokenUsage.OneTimeOnly
IdentityServer/IdentityServer4,IdentityServer/IdentityServer4,MienDev/IdentityServer4,IdentityServer/IdentityServer4,MienDev/IdentityServer4,MienDev/IdentityServer4,IdentityServer/IdentityServer4,MienDev/IdentityServer4