[Merged by Bors] - chore: reduce imports in several files

[adomani]

Found by using the output of #14840.

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[github-actions]

PR summary 05871bdaf0

Import changes for modified files

Dependency changes

File	Base Count	Head Count	Change
Mathlib.Algebra.Group.Action.Defs	282	180	-102 (-36.17%)

Import changes for all files

Files	Import difference
7 files Mathlib.Algebra.Group.Action.Option Mathlib.Algebra.GroupWithZero.Action.Defs Mathlib.Algebra.Ring.Action.Basic Mathlib.GroupTheory.GroupAction.Ring Mathlib.Algebra.Group.Action.Sigma Mathlib.Algebra.Group.Action.Sum Mathlib.Algebra.Group.Action.Defs	-102
6 files Mathlib.Algebra.Group.Action.Opposite Mathlib.Algebra.Group.Action.Units Mathlib.GroupTheory.GroupAction.Prod Mathlib.Algebra.Group.Action.Prod Mathlib.GroupTheory.GroupAction.Opposite Mathlib.Algebra.SMulWithZero	-101
Mathlib.Algebra.Order.AddTorsor	-97
Mathlib.Algebra.Group.Action.Pi Mathlib.GroupTheory.GroupAction.Pi	-88

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

[grunweg]

Nice, thanks!
maintainer merge

[github-actions]

🚀 Pull request has been placed on the maintainer queue by grunweg.

[mattrobball]

bors merge

[mathlib-bors]

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[mathlib-bors]

Pull request successfully merged into master.

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