proj: add version 9.3.1

[mayeut]

Specify library name and version: proj/9.3.1

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• I've read the contributing guidelines.
• I've used a recent Conan client version close to the currently deployed.
• I've tried at least one configuration locally with the conan-center hook activated.

[ghost]

I detected other pull requests that are modifying proj/all recipe:

• proj: add v9.4.0, drop old versions #21512

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 1 (c76d0052da2d62c6d3ea9dffc3b49e6ac7fc4fff):

• proj/9.3.1:
  All packages built successfully! (All logs)

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Conan v2 pipeline ✔️

Note: Conan v2 builds are now mandatory. Please read our discussion about it.

All green in build 1 (c76d0052da2d62c6d3ea9dffc3b49e6ac7fc4fff):

• proj/9.3.1:
  All packages built successfully! (All logs)

[conan-center-bot]

This PR has been automatically merged due to Bump version or Bump dependencies label.
Read https://github.com/conan-io/conan-center-index/blob/master/docs/labels.md#bump-version to obtain more information.