Update docs README.rst to clarify --package-filter usage

[RNHTTR]

Make the --package-filter flag a bit more clear, and demonstrate that it can be used for multiple packages.

[potiuk]

Just realized @RNHTTR@utkarsharma2@Taragolis : We have not finished switching from --package-filter to command parameters, it used to be that `--package-fllter had autocompletion and list of packages but before Summit with @amoghrajesh we moved it command option - see #35067

[github-actions]

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[potiuk]

Suggested change

	"The list of short hand names can be found in --help output "
	"Multiple package filters can be applied by passing the flag multiple times. "
	"For example --package-filter apache-airflow --package-filter apache-airflow-providers-<provider>",
	"The list of short hand names can be found in --help output "
	"Multiple package filters can be applied by passing the flag multiple times. "
	"For example --package-filter apache-airflow --package-filter apache-airflow-providers-<provider>. "
	"You can also specify glob-pattern. For example --package-filter '*providers*'." ,

[potiuk]

Approved - proposed one NIT: improvement (--package-filter allows glob pattern matching), you will akso need to apply static checks to include the description in the help screenshots.

[amoghrajesh]

LGTM +1
Test needs fixing

[RNHTTR]

Closed by: #36287