chore: update templates (#73)

* chore(python): skip docfx in main presubmit

* chore(python): skip docfx in main presubmit

* fix: properly template the repo name

Source-Author: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>
Source-Date: Fri Jan 8 10:32:13 2021 -0700
Source-Repo: googleapis/synthtool
Source-Sha: fb53b6fb373b7c3edf4e55f3e8036bc6d73fa483
Source-Link: googleapis/synthtool@fb53b6f

* chore: add missing quotation mark

Source-Author: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>
Source-Date: Mon Jan 11 09:43:06 2021 -0700
Source-Repo: googleapis/synthtool
Source-Sha: 16ec872dd898d7de6e1822badfac32484b5d9031
Source-Link: googleapis/synthtool@16ec872

* chore: add 3.9 to noxfile template

Since the python-docs-samples noxfile-template doesn't sync with this, I wanted to make sure the noxfile template matched the most recent change [here](https://github.com/GoogleCloudPlatform/python-docs-samples/pull/4968/files)

cc @tmatsuo

Source-Author: Leah E. Cole <6719667+leahecole@users.noreply.github.com>
Source-Date: Fri Jan 15 17:24:05 2021 -0800
Source-Repo: googleapis/synthtool
Source-Sha: 56ddc68f36b32341e9f22c2c59b4ce6aa3ba635f
Source-Link: googleapis/synthtool@56ddc68

* build(python): make `NOX_SESSION` optional

I added this accidentally in #889. `NOX_SESSION` should be passed down if it is set but not marked required.

Source-Author: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>
Source-Date: Tue Jan 19 09:38:04 2021 -0700
Source-Repo: googleapis/synthtool
Source-Sha: ba960d730416fe05c50547e975ce79fcee52c671
Source-Link: googleapis/synthtool@ba960d7

secretmanager/snippets/noxfile.py

@@ -85,7 +85,7 @@ def get_pytest_env_vars() -> Dict[str, str]:
 
 # DO NOT EDIT - automatically generated.
 # All versions used to tested samples.
-ALL_VERSIONS = ["2.7", "3.6", "3.7", "3.8"]
+ALL_VERSIONS = ["2.7", "3.6", "3.7", "3.8", "3.9"]
 
 # Any default versions that should be ignored.
 IGNORED_VERSIONS = TEST_CONFIG['ignored_versions']