docs(client.go): bump client version (#698)

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Author: anthony-gomez-fastly

fastly/client.go

@@ -62,7 +62,7 @@ const UserAgentEnvVar = "FASTLY_USER_AGENT"
 var ProjectURL = "github.com/fastly/go-fastly"
 
 // ProjectVersion is the version of this library.
-var ProjectVersion = "10.3.0"
+var ProjectVersion = "10.4.0"
 
 // UserAgent is the user agent for this particular client.
 var UserAgent = fmt.Sprintf("FastlyGo/%s (+%s; %s)",