Do not make Immutable matrices the target of :mod:sympy links

[eric-wieser]

.. module:: sympy means "this page is the main documentation for sympy, and resolve refs relative to sympy".
.. currentmodule:: sympy means "resolve refs relative to sympy".

As written, this caused nonsensical intersphinx links when :mod:`sympy` was used.

References to other Issues or PRs

Brief description of what is fixed or changed

Other comments

Release Notes

• other
  • intersphinx links to :mod:`sympy` no longer point to the documentation for Immutable Matrices

[sympy-bot]

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• other
  • intersphinx links to :mod:`sympy` no longer point to the documentation for Immutable Matrices (#19430 by @eric-wieser)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.7.

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`.. module:: sympy` means "this page is the main documentation for `sympy`, and resolve refs relative to `sympy`".
`.. currentmodule:: sympy` means "resolve refs relative to `sympy`".

As written, this caused nonsensical intersphinx links when `` :mod:`sympy` `` was used.

<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
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format, e.g. "Fixes #1234" (see
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open. -->


#### Brief description of what is fixed or changed


#### Other comments


#### Release Notes

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<!-- BEGIN RELEASE NOTES -->
* other
  * intersphinx links to `` :mod:`sympy` `` no longer point to the documentation for Immutable Matrices
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[codecov]

Codecov Report

Merging #19430 into master will decrease coverage by 0.023%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##            master    #19430       +/-   ##
=============================================
- Coverage   75.651%   75.628%   -0.024%     
=============================================
  Files          652       652               
  Lines       169712    169712               
  Branches     40051     40051               
=============================================
- Hits        128390    128350       -40     
- Misses       35720     35751       +31     
- Partials      5602      5611        +9