Fix malformed TOML example in Fastly setup guide (#766)

The [ec] configuration example in docs/guide/fastly.md carried stray
characters from a copy-paste artifact, leaving the snippet invalid:

    passphrase = "replace-with-32-plus-byte-random-secret"}]}},{

Remove the trailing characters so the example parses as TOML.

Co-authored-by: Christian Pavilonis <christianpavilonis@outlook.com>

Author: jwrosewell

docs/guide/fastly.md

@@ -112,7 +112,7 @@ Configure in `trusted-server.toml`:
 
 ```toml
 [ec]
-passphrase = "replace-with-32-plus-byte-random-secret"}]}},{
+passphrase = "replace-with-32-plus-byte-random-secret"
 ec_store = "ec_identity_store"
 ```