chore: Bump version to 0.40.0

[lgoettgens]

ToDo-List before merging this:

• Unify eigenvalue interface #1611 (merge missing)
• Allow polynomial rings with 0 variables #1619
• feat: remove some unsound promotion methods #1620
• bug: fix determinant of empty matrix #1628
• Remove divisible, copy documentation to is_divisible_by instead #1618
• Update finite field printing #1622 (review missing)
• Rename padics #1621 (review missing)
• Rename number_of_* functions consistently #1624 (review missing)
• Weird finite_field dispatch #1623 / Remove a weird finite_field dispatch #1625
• fix: properly GC.@preserve more objects #1626
• Remove unneeded Generic. prefixes #1635 (waiting for Export EuclideanRingResidue*Elem as well AbstractAlgebra.jl#1562)
• Adapt residue_ring and residue_field dispatches introduced in Nemo to return two things (@thofma) feat: adjustment for new residue_* convention #1636

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2fd7f02) 84.05% compared to head (07a3c75) 84.33%.
Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1634      +/-   ##
==========================================
+ Coverage   84.05%   84.33%   +0.27%     
==========================================
  Files          93       93              
  Lines       36769    39322    +2553     
==========================================
+ Hits        30908    33163    +2255     
- Misses       5861     6159     +298     

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[lgoettgens]

Let's wait for a combined CI if everything here before tagging

[lgoettgens]

We could include #1631 in this release as well. If the remaining things from the Hackmd get decided today that would not delay us by much and would make the changes propagate much faster downstream