Bump github.com/gorilla/sessions from 1.3.0 to 1.4.0

Bumps [github.com/gorilla/sessions](https://github.com/gorilla/sessions) from 1.3.0 to 1.4.0.
- [Release notes](https://github.com/gorilla/sessions/releases)
- [Commits](gorilla/sessions@v1.3.0...v1.4.0)

---
updated-dependencies:
- dependency-name: github.com/gorilla/sessions
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/gorilla/csrf v1.7.2
 	github.com/gorilla/handlers v1.5.2
 	github.com/gorilla/mux v1.8.1
-	github.com/gorilla/sessions v1.3.0
+	github.com/gorilla/sessions v1.4.0
 	github.com/kouhin/envflag v0.0.0-20150818174321-0e9a86061649
 	github.com/litao91/goldmark-mathjax v0.0.0-20210217064022-a43cf739a50f
 	github.com/mdigger/goldmark-attributes v0.0.0-20210529130523-52da21a6bf2b

go.sum

@@ -61,8 +61,8 @@ github.com/gorilla/mux v1.8.1 h1:TuBL49tXwgrFYWhqrNgrUNEY92u81SPhu7sTdzQEiWY=
 github.com/gorilla/mux v1.8.1/go.mod h1:AKf9I4AEqPTmMytcMc0KkNouC66V3BtZ4qD5fmWSiMQ=
 github.com/gorilla/securecookie v1.1.2 h1:YCIWL56dvtr73r6715mJs5ZvhtnY73hBvEF8kXD8ePA=
 github.com/gorilla/securecookie v1.1.2/go.mod h1:NfCASbcHqRSY+3a8tlWJwsQap2VX5pwzwo4h3eOamfo=
-github.com/gorilla/sessions v1.3.0 h1:XYlkq7KcpOB2ZhHBPv5WpjMIxrQosiZanfoy1HLZFzg=
-github.com/gorilla/sessions v1.3.0/go.mod h1:ePLdVu+jbEgHH+KWw8I1z2wqd0BAdAQh/8LRvBeoNcQ=
+github.com/gorilla/sessions v1.4.0 h1:kpIYOp/oi6MG/p5PgxApU8srsSw9tuFbt46Lt7auzqQ=
+github.com/gorilla/sessions v1.4.0/go.mod h1:FLWm50oby91+hl7p/wRxDth9bWSuk0qVL2emc7lT5ik=
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 h1:BQSFePA1RWJOlocH6Fxy8MmwDt+yVQYULKfN0RoTN8A=
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99/go.mod h1:1lJo3i6rXxKeerYnT8Nvf0QmHCRC1n8sfWVwXF2Frvo=
 github.com/kevinburke/ssh_config v1.2.0 h1:x584FjTGwHzMwvHx18PXxbBVzfnxogHaAReU4gf13a4=