[PT2E][Docs] Calibration is a must for both static and dynamic quantization (#4307)

* [PT2E] Run weight observer eagerly for dynamic quant

* Revert "[PT2E] Run weight observer eagerly for dynamic quant"

This reverts commit f373bd1.

* Update docs

* Update index.rst

---------

Co-authored-by: Copilot <copilot@github.com>

Author: Xia-Weiwen

docs/source/pt2e_quantization/index.rst

@@ -52,7 +52,9 @@ API Example::
   m = prepare_pt2e(m, quantizer)
 
   # run calibration
+  # must run calibration for both static and dynamic quantization
   # calibrate(m, sample_inference_data)
+
   m = convert_pt2e(m)
 
   # Step 3. lowering