Fix eachdist dependency version matching

[HasanTasdiq]

Fixes #5227

Summary

• Tightened the dependency version replacement regex in scripts/eachdist.py.
• Prevented package names that are prefixes of another package, such as opentelemetry-proto, from matching opentelemetry-proto-json.
• Added the towncrier changelog fragment for this release-tooling fix.

Why

The release helper matched package name prefixes too broadly, so updating opentelemetry-proto could also rewrite dependencies for opentelemetry-proto-json.

Testing

• Ran: targeted Python validation snippet for update_dependencies and update_patch_dependencies using temporary pyproject.toml fixtures - passed
• Ran: python3 -m py_compile scripts/eachdist.py - passed

Notes

• Full tox/precommit not run locally because uv and tox are not installed in this shell.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: HasanTasdiq / name: Tasdiqul (1b430ec, c3e3dcb)

[xrmx]

I think the regexp can be simplified by assuming there's only whitespace between package name and version.