fix: typo and improve description

[zaerald]

This PR fixes the typo with "the the", and elaborated the description for @ComponentScan.

Motivation
For updating the description of @ComponentScan. Beginners, like me, uses Spring guides, and it was confusing as to why the com.example.testingweb package gets picked, and the reason it was picked as the package of the class annotated with @SpringBootApplication.

Feel free to correct me, to improve this part. This can also open new idea if we can add new macro (https://github.com/spring-guides/getting-started-macros) for the @SpringBootApplication annotation.
They could be found in other guides (not exhaustive list):

• https://spring.io/guides/gs/rest-service/
• https://spring.io/guides/gs/uploading-files/
• https://spring.io/guides/gs/accessing-data-neo4j/

[adilwahla]

looks okay 👍