[BUG] Fail to set ACL policy file with etag which is got from `Get` API

[KanShiori]

go version: 1.24.0
version tailscale.com/client/tailscale/v2 v2.0.0-20250509161557-5fad10cf3a33

My code is like:

acl, err := ts.PolicyFile().Get(context.TODO())
Expect(err).To(BeNil())

// modify acl here

err = ts.PolicyFile().Set(context.TODO(), *acl, acl.ETag)
Expect(err).To(BeNil())

And I got an error: precondition failed, invalid old hash (412).

The root cause is using fmt.Sprintf("%q", etag) to set the etag header in the Set function, it adds extra double quotes.

tailscale-client-go-v2/policyfile.go

Line 201 in 5fad10c

headers["If-Match"] = fmt.Sprintf("%q", etag)

So, now I have to remove double quotes before calling the Set function, like:

etag := strings.Trim(acl.ETag, "\"")
err = ts.PolicyFile().Set(context.TODO(), *acl, etag)