refactor: golf Analytic/IteratedFDeriv, SpecialFunctions/

[yuanyi-350]

This PR ports the changes from #37968 restricted to the following files:

• Mathlib/Analysis/Analytic/IteratedFDeriv.lean
• Mathlib/Analysis/SpecialFunctions/Gaussian/FourierTransform.lean
• Mathlib/Analysis/SpecialFunctions/Gamma/Basic.lean

Only these selected file changes are included.

[github-actions]

PR summary 14ec76b5f0

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

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/pr_summary/declarations_diff.sh <optional_commit>

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

The doc-module for scripts/pr_summary/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/reporting/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[github-actions]

✅ PR Title Formatted Correctly

The title of this PR has been updated to match our commit style conventions.
Thank you!

[grunweg]

Please follow the request made in the comments here and here. Thanks!