Remove what is about deploying behind Gitea (closes #209)

Delete the Gitea compose setup, its document, its two scripts and their
make targets. Documents and tests no longer use Gitea as the example
deployment. The Core Rule Set exclusions for Gitea's false positives in
internal/waf stay, with their comments and tests.

Model: opus-5-5

internal/servewaf/requestlog_test.go

@@ -19,7 +19,7 @@ const (
 	// requestIDHeader carries the request's id.
 	requestIDHeader = "X-Request-ID"
 	// instance is the SWWAF_INSTANCE_NAME a test sets.
-	instance = "fsn1app1/gitea"
+	instance = "fsn1app1/blog"
 	// ipv6Client is a client on IPv6, and ipv6Group the netblock the rate
 	// limits count it as.
 	ipv6Client = "2001:db8::7"