www/waterfox: Upstream silently replace distfiles

No functional changes - full diff is:

• waterfox-6.6.0-beta-3.old/testing/web-platform/tests/tools/third_party/attrs/.git_archival.txt

+++ waterfox-6.6.0-beta-3/testing/web-platform/tests/tools/third_party/attrs/.git_archival.txt
@@ -1,4 +1,4 @@
node: a5bcba70a19f96ddb5e29ee0229f2324dab364ab
node-date: 2025-07-24T17:43:44+01:00
describe-name: 6.6.0-beta-3
-ref-names: tag: 6.6.0-beta-3, future
+ref-names: tag: 6.6.0-beta-3

PR: 288470
MFH: 2025Q3
(cherry picked from commit b3542651e0604a142be8407db2e064d992388889)