v5.5.1

Symbolics v5.5.1

Diff since v5.5.0

Closed issues:

• Inv does not work for a constant 1x1 matrix after updating to Symbolics v5.3.1 (#895)
• move Sympy.jl to extension? (#922)

Merged pull requests:

• Fixes #895 (#896) (@Gregstrq)
• MultithreadedForm can cause deadlock (#914) (@YingboMa)
• SymPy 1.9 pkg extension (#923) (@longemen3000)
• Type asserts for hash, _iszero, and _isone (#927) (@chriselrod)
• bump Groebner (#935) (@sumiya11)