Update tox to 3.13.2 (#11764)

Update tox to 3.13.2

requirements/travis_base.txt

@@ -7,9 +7,9 @@ wheel==0.33.4 \
 setuptools==41.0.1 \
     --hash=sha256:a222d126f5471598053c9a77f4b5d4f26eaa1f150ad6e01dcf1a42e185d05613 \
     --hash=sha256:c7769ce668c7a333d84e17fe8b524b1c45e7ee9f7908ad0a73e1eda7e6a5aebf
-tox==3.13.1 \
+tox==3.13.2 \
-    --hash=sha256:45a265e953368fb372cca3eac33b69fdb1b1453e5b114be231c84fc3dfadceed \
+    --hash=sha256:dab0b0160dd187b654fc33d690ee1d7bf328bd5b8dc6ef3bb3cc468969c659ba \
-    --hash=sha256:f5cb0b5b8d14f2100982b0981c750d840228180a348e6bad355aa38e949fbc3f
+    --hash=sha256:ee35ffce74933a6c6ac10c9a0182e41763140a5a5070e21b114feca56eaccdcd
 
 # Dependencies of Tox
 virtualenv==16.6.1 \