Fix some issues reported by lintian

Fix some issues reported by lintian

• debian/copyright: use spaces rather than tabs to start continuation lines. (tab-in-license-text)
• Set upstream metadata fields: Bug-Database, Bug-Submit, Repository, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking, upstream-metadata-missing-repository)
• Set upstream metadata fields: Security-Contact.

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Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/python-jsonschema/20984670-eed4-4dbc-9657-4a49437833b1.

Debdiff

These changes affect the binary packages:

[The following lists of changes regard files as different if they have different names, permissions or owners.]

Files in second set of .debs but not in first

lrwxrwxrwx  root/root   /usr/share/doc/python-jsonschema-doc/html/_static/language_data.js -> ../../../../javascript/sphinxdoc/1.0/language_data.js

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/share/doc/python-jsonschema-doc/html/_static/language_data.js

Control files of package python-jsonschema-doc: lines which differ (wdiff format)

• Depends: libjs-sphinxdoc (>= 1.0) 2.4.3-5~)

No differences were encountered between the control files of package **python3-jsonschema**

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