render func.now() as CURRENT_TIMESTAMP

[sfc-gh-sfan]

Please answer these questions before submitting your pull requests. Thanks!

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes #NNNN

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
   • I am adding new logging messages
   • I am adding new credentials
   • I am adding a new dependency

3. Please describe how your code solves the related issue.

   Please write a short description of how your code change solves the related issue.

[codecov]

Codecov Report

Merging #397 (5c8d489) into main (63e5e20) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
+ Coverage   81.25%   81.28%   +0.02%     
==========================================
  Files          10       10              
  Lines        1275     1277       +2     
  Branches      192      192              
==========================================
+ Hits         1036     1038       +2     
  Misses        176      176              
  Partials       63       63              

Impacted Files	Coverage Δ
src/snowflake/sqlalchemy/base.py	91.79% <100.00%> (+0.06%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more