[libidn2] Update to 2.3.1

[lazyhamster]

Describe the pull request

• What does your PR fix?

  Updates libidn2 to version 2.3.1

• Which triplets are supported/not supported? Have you updated the CI baseline?

  Same as before, Yes

• Does your PR follow the maintainer guide?

  Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

  Yes

[github-actions]

This is a new experimental fast check for PR issues. Please let us know if this bot is helpful!

After committing all other changes, the version database must be updated

git add -u && git commit
git checkout 7e7dad5fe20cdc085731343e0e197a7ae655555b -- versions
./vcpkg x-add-version --all

Diff

diff --git a/versions/l-/libidn2.json b/versions/l-/libidn2.json
index 177c331..1917ca6 100644
--- a/versions/l-/libidn2.json
+++ b/versions/l-/libidn2.json
@@ -1,7 +1,7 @@
 {
   "versions": [
     {
-      "git-tree": "e2fff10cb4bcf876ccee67ace991174180bfa957",
+      "git-tree": "639f3ae3abc9b7265de12b29bfefb49a683e0b53",
       "version": "2.3.1",
       "port-version": 0
     },

You have modified or added at least one vcpkg.json where a "license" field is missing.
If you feel able to do so, please consider adding a "license" field to the following files:

• ports/libidn2/vcpkg.json

Valid values for the license field are listed at https://spdx.org/licenses/

[github-actions]

You have modified or added at least one vcpkg.json where a "license" field is missing.
If you feel able to do so, please consider adding a "license" field to the following files:

• ports/libidn2/vcpkg.json

Valid values for the license field are listed at https://spdx.org/licenses/

[ras0219-msft]

Thanks for the update!