gnu: python-google-cloud-core: Fix tests on python-3.12.

* gnu/packages/python-web.scm (python-google-cloud-core) [arguments]
<test-flags>: Ignore faileur on deprecation warning.

Change-Id: I4657321d9fd72dd2b6b8cb09a197b2c92fbc2ad8

gnu/packages/python-web.scm

@@ -12415,6 +12415,14 @@ the @code{googleapis/api-common-protos} repository.")
        (sha256
         (base32 "1d7li74cakgl9vghxfir9nxwy36980alvxwgwjg0zyla3hgj07cq"))))
     (build-system pyproject-build-system)
+    (arguments
+     (list
+      #:test-flags
+      ;; XXX: DeprecationWarning: datetime.datetime.utcfromtimestamp() is
+      ;; deprecated and scheduled for removal in a future version. Use
+      ;; timezone-aware objects to represent datetimes in UTC:
+      ;; datetime.datetime.fromtimestamp(timestamp, datetime.UTC).
+      #~(list "-W" "ignore::DeprecationWarning")))
     (propagated-inputs (list python-google-api-core python-google-auth))
     (native-inputs
      (list python-grpcio