chore(deps): update dependency keyring to v25.6.0 (#565)

Author: renovate-bot

.kokoro/requirements.txt

@@ -360,9 +360,9 @@ Jinja2==3.1.5 \
     --hash=sha256:8fefff8dc3034e27bb80d67c671eb8a9bc424c0ef4c0826edbff304cceff43bb \
     --hash=sha256:aba0f4dc9ed8013c424088f68a5c226f7d6097ed89b246d7749c2ec4175c6adb
     # via gcp-releasetool
-keyring==25.5.0 \
-    --hash=sha256:4c753b3ec91717fe713c4edd522d625889d8973a349b0e582622f49766de58e6 \
-    --hash=sha256:e67f8ac32b04be4714b42fe84ce7dad9c40985b9ca827c592cc303e7c26d9741
+keyring==25.6.0 \
+    --hash=sha256:0b39998aa941431eb3d9b0d4b2460bc773b9df6fed7621c2dfb291a7e0187a66 \
+    --hash=sha256:552a3f7af126ece7ed5c89753650eec89c7eaae8617d0aa4d9ad2b75111266bd
     # via
     #   gcp-releasetool
     #   twine