golangci-lint: disable canonicalheader

canonicalheader v1.1.2 nil-derefs on a package that has both a generic
method and an http.Header.Set call, which aborts the whole lint run.

.golangci.yaml

@@ -3,6 +3,10 @@ version: "2"
 linters:
   default: all
   disable:
+    # canonicalheader v1.1.2 panics (nil deref) on a generic method in a
+    # package that also calls http.Header.Set. Re-enable once golangci-lint
+    # ships a version that parses Go 1.27 generic methods.
+    - canonicalheader
     - cyclop
     - depguard
     - dupl