feat: in show {package} output, clarify meaning of 'required by' entries

[elliot-100]

Pull Request Check List

Resolves: #9749

• Added tests for changed code.
• Updated documentation for changed code

Example of actual output before:

> poetry show requests
 name         : requests
 version      : 2.32.3
 description  : Python HTTP for Humans.

dependencies
 - certifi >=2017.4.17
 - charset-normalizer >=2,<4
 - idna >=2.5,<4
 - urllib3 >=1.21.1,<3

required by
 - cachecontrol >=2.16.0

After:

> poetry show requests
 name         : requests
 version      : 2.32.3
 description  : Python HTTP for Humans.

dependencies
 - certifi >=2017.4.17
 - charset-normalizer >=2,<4
 - idna >=2.5,<4
 - urllib3 >=1.21.1,<3

required by
 - cachecontrol requires requests >=2.16.0

[elliot-100]

pre-commit.ci autofix

[elliot-100]

Thank you!