Update dependency rdflib to v5

[renovate]

This PR contains the following updates:

Package	Update	Change
rdflib	major	==4.2.2 -> ==5.0.0

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Release Notes

RDFLib/rdflib

v5.0.0

Compare Source

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5.0.0 is a major stable release and is the last release to support Python 2 & 3.4. 5.0.0 is mostly backwards-
compatible with 4.2.2 and is intended for long-term, bug fix only support.

5.0.0 comes two weeks after the 5.0.0RC1 and includes a small number of additional bug fixes. Note that
rdflib-jsonld has released a version 0.5.0 to be compatible with rdflib 5.0.0.

All PRs merged since 5.0.0RC1:

General Bugs Fixed:

• Fix n3 parser exponent syntax of floats with leading dot.
  PR #​1012
• FIX: Change is comparison to == for tuple
  PR #​1009
• fix #​913 : Added _parseBoolean function to enforce correct Lexical-to-value mapping
  PR #​995

Enhanced Features:

• Issue 1003
  PR #​1005

SPARQL Fixes:

• CONSTRUCT resolve with initBindings fixes #​1001
  PR #​1002

Documentation Fixes:

• DOC: Use sphinxcontrib-apidoc and various cleanups
  PR #​1010
• Update copyright year in docs conf.py
  PR #​1006
• slightly improved styling, small index text changes
  PR #​1004

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