Update pnpm version to latest stable 9.15.4

[spwoodcock]

What type of PR is this? (check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation
• 🧑‍💻 Refactor
• ✅ Test
• 🤖 Build or CI
• ❓ Other (please specify)

Related Issue

Hopefully fixes #2087

Describe this PR

• Updated pnpm version to latest stable, in an attempt to fix segfault issue in linked PR.
• If this doesn't solve it, then we need to dig into dependencies.
• The default version of pnpm used is now 9.15.4 and probably mandatory due to corepack and packageManager in package.json. (cc @NSUWAL123)

Checklist before requesting a review

• 📖 Read the FMTM Contributing Guide: https://github.com/hotosm/fmtm/blob/main/CONTRIBUTING.md
• 📖 Read the HOT Code of Conduct: https://docs.hotosm.org/code-of-conduct
• 👷‍♀️ Create small PRs. In most cases, this will be possible.
• ✅ Provide tests for your changes.
• 📝 Use descriptive commit messages.
• 📗 Update any related documentation and include any relevant screenshots.

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