chore: don't have golangci-lint update go.mod in CI (italia#374)

.golangci.yaml

@@ -1,4 +1,17 @@
 run:
+  # If set, we pass it to "go list -mod={option}". From "go help modules":
+  # If invoked with -mod=readonly, the go command is disallowed from the implicit
+  # automatic updating of go.mod described above. Instead, it fails when any changes
+  # to go.mod are needed. This setting is most useful to check that go.mod does
+  # not need updates, such as in a continuous integration and testing system.
+  # If invoked with -mod=vendor, the go command assumes that the vendor
+  # directory holds the correct copies of dependencies and ignores
+  # the dependency descriptions in go.mod.
+  #
+  # Allowed values: readonly|vendor|mod
+  # Default: ""
+  modules-download-mode: readonly
+
   # Include test files or not.
   # Default: true
   tests: false