Mention that Python is now 64 bits in change log (#19360)
Fix-up of #18591
### Summary of the issue:
Everybody knows that we have moved from 32-bit Python to 64-bit Python.
But it seems that it isn't written anywhere in the change log.
### Description of user facing changes:
* Add the architecture detail in the Python version change log item.
* While at it, converted a no-break space to a normal space since normal
spaces were used everywhere else.
### Description of developer facing changes:
None
### Description of development approach:
None
### Testing strategy:
Check the generated file.
### Known issues with pull request:
None
