go.mod: bump gorilla/csrf for security fix (#14822)

For https://github.com/gorilla/csrf/commit/9dd6af1f6d30fc79fb0d972394deebdabad6b5eb

Update client/web and safeweb to correctly signal to the csrf middleware
whether the request is being served over TLS. This determines whether
Origin and Referer header checks are strictly enforced. The gorilla
library previously did not enforce these checks due to a logic bug based
on erroneous use of the net/http.Request API. The patch to fix this also
inverts the library behavior to presume that every request is being
served over TLS, necessitating these changes.

Updates tailscale/corp#25340

Signed-off-by: Patrick O'Doherty <patrick@tailscale.com>
Co-authored-by: Patrick O'Doherty <patrick@tailscale.com>

go.sum

@@ -529,8 +529,8 @@ github.com/goreleaser/fileglob v1.3.0 h1:/X6J7U8lbDpQtBvGcwwPS6OpzkNVlVEsFUVRx9+
 github.com/goreleaser/fileglob v1.3.0/go.mod h1:Jx6BoXv3mbYkEzwm9THo7xbr5egkAraxkGorbJb4RxU=
 github.com/goreleaser/nfpm/v2 v2.33.1 h1:EkdAzZyVhAI9JC1vjmjjbmnNzyH1J6Cu4JCsA7YcQuc=
 github.com/goreleaser/nfpm/v2 v2.33.1/go.mod h1:8wwWWvJWmn84xo/Sqiv0aMvEGTHlHZTXTEuVSgQpkIM=
-github.com/gorilla/csrf v1.7.2 h1:oTUjx0vyf2T+wkrx09Trsev1TE+/EbDAeHtSTbtC2eI=
-github.com/gorilla/csrf v1.7.2/go.mod h1:F1Fj3KG23WYHE6gozCmBAezKookxbIvUJT+121wTuLk=
+github.com/gorilla/csrf v1.7.3-0.20250123201450-9dd6af1f6d30 h1:fiJdrgVBkjZ5B1HJ2WQwNOaXB+QyYcNXTA3t1XYLz0M=
+github.com/gorilla/csrf v1.7.3-0.20250123201450-9dd6af1f6d30/go.mod h1:F1Fj3KG23WYHE6gozCmBAezKookxbIvUJT+121wTuLk=
 github.com/gorilla/securecookie v1.1.2 h1:YCIWL56dvtr73r6715mJs5ZvhtnY73hBvEF8kXD8ePA=
 github.com/gorilla/securecookie v1.1.2/go.mod h1:NfCASbcHqRSY+3a8tlWJwsQap2VX5pwzwo4h3eOamfo=
 github.com/gostaticanalysis/analysisutil v0.7.1 h1:ZMCjoue3DtDWQ5WyU16YbjbQEQ3VuzwxALrpYd+HeKk=