Update omniauth-oauth due to rack v3 compatibility issues

Author: unasuke

Gemfile.lock

@@ -359,9 +359,10 @@ GEM
     omniauth-github (2.0.1)
       omniauth (~> 2.0)
       omniauth-oauth2 (~> 1.8)
-    omniauth-oauth (1.2.0)
+    omniauth-oauth (1.2.1)
       oauth
       omniauth (>= 1.0, < 3)
+      rack (>= 1.6.2, < 4)
     omniauth-oauth2 (1.8.0)
       oauth2 (>= 1.4, < 3)
       omniauth (~> 2.0)