Remove the CrowdSec decision feed (closes #315)

sneak ruled to remove it. Gone: the heuristic crowdsec, the ban cause
crowdsec and its earlier_bans count, the tag crowdsec, the settings
SWW_WAF_CROWDSEC_LAPI_URL and SWW_WAF_CROWDSEC_LAPI_KEY, the decision
list fetch and parse in internal/reputation, their tests, and every
mention in the README, SPEC.md and docs/. EVALUATION.md keeps its
comparison of tools.

The ban ledger's internal ban function loses its expires parameter,
which only CrowdSec bans used.

Model: opus-5-5

internal/waf/reputation.go

@@ -1,7 +1,6 @@
 package waf
 
-// What the reputation heuristics share: blocklists, crowdsec, dnsbl and
-// abuseipdb.
+// What the reputation heuristics share: blocklists, dnsbl and abuseipdb.
 
 import (
 	"sneak.berlin/go/smallwebwaf/internal/alerts"