update travis for s3

.travis.yml

@@ -20,6 +20,8 @@ deploy:
     branch: master
     condition: $TRAVIS_OTP_RELEASE = R16B03-1
   provider: s3
+  edge:
+    branch: s3-backward-compat
   access_key_id: AKIAJAPYAQEFYCYSNL7Q
   secret_access_key:
     secure: "BUv2KQABv0Q4e8DAVNBRTc/lXHWt27yCN46Fdgo1IrcSSIiP+hq2yXzQcXLbPwkEu6pxUZQtL3mvKbt6l7uw3wFrcRfFAi1PGTITAW8MTmxtwcZIBcHSk3XOzDbkK+fYYcaddszmt7hDzzEFPtmYXiNgnaMIVeynhQLgcCcIRRQ="