Upgrade golangci-lint (#182)

1.42 seems to be having some problems with Go 1.18 (see #2649), so let's
just upgrade to latest.  There was one new error, suggesting to use `%q`
rather than `"%s"`, since the former does escapes properly.  It doesn't
really matter for us -- the string should be an identifier -- but it
doesn't hurt.  (Plus it wanted us to upgrade from ioutil, which I did
in #181.)

Test plan: make check

internal/lint/go.mod

@@ -1,6 +1,6 @@
 module github.com/Khan/genqlient/internal/lint
 
-go 1.14
+go 1.16
 
 // Should match golangci-lint version in .github/workflows/go.yml
-require github.com/golangci/golangci-lint v1.42.0
+require github.com/golangci/golangci-lint v1.45.0