Revert "Support SAML authentication (#25165)" (#29358)

This reverts #25165 (5bb8d1924d), as there
was a chance some important reviews got missed.

so after reverting this patch it will be resubmitted for reviewing again

https://github.com/go-gitea/gitea/pull/25165#issuecomment-1960670242

temporary Open #5512 again

routers/web/web.go

@@ -667,11 +667,6 @@ func registerRoutes(m *web.Route) {
 			m.Get("/{provider}", auth.SignInOAuth)
 			m.Get("/{provider}/callback", auth.SignInOAuthCallback)
 		})
-		m.Group("/saml", func() {
-			m.Get("/{provider}", auth.SignInSAML) // redir to SAML IDP
-			m.Post("/{provider}/acs", auth.SignInSAMLCallback)
-			m.Get("/{provider}/metadata", auth.SAMLMetadata)
-		})
 	})
 	// ***** END: User *****