[misc] Add flag to disable taichi header print (taichi-dev#8413)

Issue: taichi-dev#8334 

### Brief Summary

Add a flag to disable Taichi header print. One can set
``os.environ['ENABLE_TAICHI_HEADER_PRINT'] = False`` to disable the
header print.

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### <samp>🤖[[deprecated]](https://githubnext.com/copilot-for-prs-sunset)
Generated by Copilot at 65548e0</samp>

Add an option to disable Taichi header printing using an environment
variable. Modify `python/taichi/_lib/utils.py` to implement the option.

### Walkthrough

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### <samp>🤖[[deprecated]](https://githubnext.com/copilot-for-prs-sunset)
Generated by Copilot at 65548e0</samp>

* Add a conditional check to enable or disable the Taichi header
printing
([link](https://github.com/taichi-dev/taichi/pull/8413/files?diff=unified&w=0#diff-46daba8967b07b778d2090c80d91720ba234f327d62bc475b2fb956c9f04223dL172-R173))
* Use an environment variable `ENABLE_TAICI_HEADER_PRINT` to control the
check
([link](https://github.com/taichi-dev/taichi/pull/8413/files?diff=unified&w=0#diff-46daba8967b07b778d2090c80d91720ba234f327d62bc475b2fb956c9f04223dL172-R173))

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

python/taichi/_lib/utils.py

@@ -169,7 +169,8 @@ def _print_taichi_header():
     print(header)
 
 
-_print_taichi_header()
+if os.environ.get("ENABLE_TAICHI_HEADER_PRINT", True):
+    _print_taichi_header()
 
 
 def try_get_wheel_tag(module):