Update Blackbird submission text (XanaduAI#718)

* add link to compilers

* update for postfix release

* update link

* update link

* add html tag

Borealis (XanaduAI#714)

* bump version and requirements

* refactor tdm

* update compilers

* update core functionality

* update utilities

* update tests

* update changelog

* fix changelog

* update docs

* Update doc/introduction/photonic_hardware.rst

* Apply suggestions from code review

Co-authored-by: Josh Izaac <[email protected]>

Incrementing the version number to 0.22.0 (XanaduAI#696)

* bump version and update changelog

* update changelog

* Update .github/CHANGELOG.md

Co-authored-by: Sebastián Duque Mesa <[email protected]>

* update changelog

Co-authored-by: Sebastián Duque Mesa <[email protected]>

Increment version number to 0.21.0 (XanaduAI#666)

* bump version

* bump tw requirement

Increment version to 0.20.0 (XanaduAI#657)

* bump release

* update tw requirement

Increment version to 0.19.0 (XanaduAI#630)

* bump version number

* update changelog

* add upload workflow

* add td3 to changelog

* pin blackbird

* Add Eli Bourassa contribution

* minor updates

* more minor updates

Co-authored-by: Sebastián Duque Mesa <[email protected]>

Change simulon target to simulon_gaussian (XanaduAI#576)

**Context:**
The Xanadu Quantum Cloud simulator, formerly called `simulon`, now has the target name `simulon_gaussian`. This change was made to support many different simulon types in the future.

**Description of the Change:**
- References to `simulon` in documentation and tests have been changed to `simulon_gaussian`.
- A formatting change is made in `strawberryfields/backends/gaussianbackend/gaussiancircuit.py`. It appears that the black version on CI has been upgraded since the last commit, which now checks new elements in docstrings. This change has been made here instead of in a separate PR.

**Benefits:**
People reading the docs will not try to submit jobs to a simulator that doesn't exist 🙂

**Possible Drawbacks:**
n/a

**Related GitHub Issues:**
n/a

Removing shared ops (XanaduAI#573)

* removes unused variables in test_tdmprogram

* updates test_decompositions_integration

* updates ops.py

* updates decompositions.py

* updates backends/__init__py

* updates states.py

* updates strawberryfields/backends/gaussianbackend/gaussiancircuit.py

* updates  strawberryfields/backends/bosonicbackend/backend.py

* updates strawberryfields/backends/gaussianbackend/backend.py

* deletes shared_ops and its tests

* Fixes williamson

* unused import removed

* unused import removed

* updates backends/__init__.py

* updates requirement.txt setup.py and CHANGELOG

* Update strawberryfields/backends/__init__.py

* Update .github/CHANGELOG.md

* black

* update test suite

* update changelog

* fix

* fix

* fix

* fix

* fix

Co-authored-by: Josh Izaac <[email protected]>

Increment version number to v0.17.0 (XanaduAI#523)

* bump version and update changelog

* update about

* remove old current release

* minor tweaks

Update deprecated function names from TW (XanaduAI#472)

* Update deprecated name from TW

* update changelog

Co-authored-by: Josh Izaac <[email protected]>