Docs: simplify language use for "Working with Transactions and the DBAPI"

Docs: simplify language use for "Working with Transactions and the DBAPI"

This is my first pull request to sqlalchemy. It changes the writing style of two paragraphs in the unified tutorial [here](https://docs.sqlalchemy.org/en/20/tutorial/dbapi_transactions.html#working-with-transactions-and-the-dbapi). My goals were to.
1. Make them easier to read
2. Not change the meaning of the text.
3. Get feedback on whether this type of contribution is considered useful for sqlalchemy.

If this is a useful type of contribution, it might be good to discuss some general guidelines for me to adhere to as I continue. For instance:
- Prefer using present simple tense
- Remove superfluous words where possible
- Keep the pull requests to one or two h2 sections at a time, to make the review easier

This pull request is:

- [x] A documentation / typographical / small typing error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

I'm curious to hear what you all think. **Have a nice day!**

Closes: #11541
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/11541
Pull-request-sha: 3179690e6a5b47de99a4486a7a15cffbfacd380b

Change-Id: I9b47f6ce4fd00c44c4b0e19957acf250f5e46d2f
(cherry picked from commit fc2cb4496d35c0b8bb7d59aa74b553f07210eded)