chore(deps): bump virtualenv in /.kokoro/docker/docs (#261)

Author: dependabot[bot]

.kokoro/docker/docs/requirements.txt

@@ -32,7 +32,7 @@ platformdirs==4.2.0 \
     --hash=sha256:0614df2a2f37e1a662acbd8e2b25b92ccf8632929bc6d43467e17fe89c75e068 \
     --hash=sha256:ef0cc731df711022c174543cb70a9b5bd22e5a9337c8624ef2c2ceb8ddad8768
     # via virtualenv
-virtualenv==20.25.1 \
-    --hash=sha256:961c026ac520bac5f69acb8ea063e8a4f071bcc9457b9c1f28f6b085c511583a \
-    --hash=sha256:e08e13ecdca7a0bd53798f356d5831434afa5b07b93f0abdf0797b7a06ffe197
-    # via nox
+virtualenv==20.26.6 \
+    --hash=sha256:280aede09a2a5c317e409a00102e7077c6432c5a38f0ef938e643805a7ad2c48 \
+    --hash=sha256:7345cc5b25405607a624d8418154577459c3e0277f5466dd79c49d5e492995f2
+    # via nox