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

docs/rules.md

@@ -55,10 +55,10 @@ empty-agent      user_agent  log     ^$
 ## A file of your own
 
 `servewaf` reads the rule files in its own container. Rules of your own go in a
-file named to sort after the default, such as `50-gitea.rules`:
+file named to sort after the default, such as `50-site.rules`:
 
 ```
-# 50-gitea.rules: WordPress probes, which gitea never serves
+# 50-site.rules: WordPress probes, which this site never serves
 wp-probe         path        ban     (?i)^/(wp-login\.php|xmlrpc\.php|wp-admin/)
 ```
 
@@ -66,7 +66,7 @@ A `Dockerfile` built on the `smallwebwaf` image, for `servewaf` to run from,
 adds it:
 
 ```dockerfile
-COPY 50-gitea.rules /etc/smallwebwaf/rules.d/50-gitea.rules
+COPY 50-site.rules /etc/smallwebwaf/rules.d/50-site.rules
 ```
 
 Or mount it there. A `path` rule applies on every site behind that `servewaf`.