fix: do not count un-deprecations in Mathlib/Deprecated

[adomani]

Reported on Zulip

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[github-actions]

PR summary 035c73548d

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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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>

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

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Increase in tech debt: (relative, absolute) = (1.00, 0.01)

Current number	Change	Type
71	1	disabled deprecation lints

Current commit 035c73548d
Reference commit d51f67b0be

You can run this locally as

./scripts/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).

[Vierkantor]

I left a suggestion but it looks good enough to me either way, thanks!

bors d+

[mathlib-bors]

✌️ adomani can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

[adomani]

Given how the discussion evolved in the Zulip chat, I am going to extract this using a variation of

# count total number of `set_option linter.deprecated false`
deprecs="$(git grep -c "set_option linter.deprecated false" | awk -F: 'BEGIN{total=0} {total+=$2} END{print total}')"

# count the `linter.deprecated` exceptions that are themselves ones that are followed by `deprecated ...(since`
doubleDeprecs="$(git grep -A1 "set_option linter.deprecated false" | grep -c "deprecated .*(since")"

echo "$(( deprecs - doubleDeprecs ))"

that only searches outside the Deprecated dir.