[hotfix][docs] Imporve the correctness in Detecting Patterns doc

[KarmaGYZ]

What is the purpose of the change

This pr is to fix type, incorrect type and the result of example in Detecting Patterns in Tables doc

Brief change log

• Correct the type of symbol
• Add a missing line in the result of the example of Greedy & Reluctant Quantifiers
• Add missing blank

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[twalthr]

Thank you @KarmaGYZ. I will merge this together with a bunch of other typos that I just found.