Build(deps): Bump thewalrus from 0.20.0 to 0.21.0

[dependabot[bot]]

Bumps thewalrus from 0.20.0 to 0.21.0.

Release notes

Sourced from thewalrus's releases.

Release 0.21.0

New features

• Adds the Takagi decomposition [(#363)](XanaduAI/thewalrus#363)

• Adds the Montrealer and Loop Montrealer functions [(#363)](XanaduAI/thewalrus#374).

Improvements

• Tighten power-trace bound of odd loop Hafnian. [(#362)](XanaduAI/thewalrus#362)

• Simplifies the internal working of Bloch-Messiah decomposition [(#363)](XanaduAI/thewalrus#338).

• Simplifies the internal working of Williamson decomposition [(#366)](XanaduAI/thewalrus#338).

• Improves the handling of an edge case in Takagi [(#373)](XanaduAI/thewalrus#373).

• Adds extra tests for the Takagi decomposition [(#377)](XanaduAI/thewalrus#377)

Contributors

This release contains contributions from (in alphabetical order):

Yanic Cardin (@​yaniccd), Gregory Morse (@​GregoryMorse), Nicolas Quesada (@​nquesada)

Commits

• 544c457 bump version to 0.21.0 (#378)
• 2268bf0 Adds extra degenerate tests with nonvac nullspace (#377)
• 8ec2172 Implements the Montrealer (#374)
• 0e163bf Update symplectic.py (#372)
• e999e49 Better way to determine if a matrix is a phase times a real matrix (#373)
• 8e43ac1 Tighten power-trace bound of odd loop Hafnian (#362)
• 01fb78c Simpler and more elegant implementation of Williamson (#366)
• 6c4de00 Update decompositions.py and readds the Takagi decomposition (#363)
• d1b4922 Refactor sphinx config and bump docs python version (#364)
• 43757a9 Incrementing the version number to 0.21.0-dev (#360)
• See full diff in compare view

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