Enable gocritic equalFold and fix issues (#34952)

Continuation of https://github.com/go-gitea/gitea/pull/34678.

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Signed-off-by: silverwind <me@silverwind.io>

.golangci.yml

@@ -50,6 +50,8 @@ linters:
       require-explanation: true
       require-specific: true
     gocritic:
+      enabled-checks:
+        - equalFold
       disabled-checks:
         - ifElseChain
         - singleCaseSwitch # Every time this occurred in the code, there was no other way.