Update to Go 1.25, fix go vet errors

conn.go

@@ -86,7 +86,7 @@ func (c *Conn) EntryErr(pri Priority, msg string, attrs []Attr) error {
 	a = append(a, c.Common...)
 	a = append(a, attrs...)
 	err := c.WriteAttrs(a)
-	slices.Delete(a, 0, len(a)) // ensure GC doesn't see refs to old data
+	a = slices.Delete(a, 0, len(a)) // ensure GC doesn't see refs to old data
 	c.atts.Put(a)
 	return err
 }
@@ -97,7 +97,7 @@ func (c *Conn) WriteAttrs(attrs []Attr) error {
 	buf := c.bufs.Get().(*net.Buffers)
 	*buf = (*buf)[:0]
 	err := WireWrite(buf, c.s, attrs)
-	slices.Delete(*buf, 0, len(*buf)) // ensure GC doesn't see refs to old data
+	*buf = slices.Delete(*buf, 0, len(*buf)) // ensure GC doesn't see refs to old data
 	c.bufs.Put(buf)
 	return err
 }