Revert Node 24.14.1 pin when npm ci 0xDEAD bug is fixed in a newer Node version

## Context

Node 24.15 introduced a bug where `npm ci` exits with code 57005 (0xDEAD), breaking aspnetcore builds in the VMR unified build pipeline.

As a workaround:
- **dotnet/dotnet**: Node version pinned to 24.14.1 in `eng/pipelines/templates/jobs/vmr-build.yml`
- **dotnet/aspnetcore**: PR https://github.com/dotnet/aspnetcore/pull/66465 applies a similar workaround

## Action needed

When a new Node version is available that fixes the npm ci bug:
1. Update `eng/pipelines/templates/jobs/vmr-build.yml` in dotnet/dotnet to use the new version (or revert to `24.x`)
2. Revert https://github.com/dotnet/aspnetcore/pull/66465
3. Close this issue

## Impact

This bug has been blocking all main branch rolling builds (public + internal) since ~April 20, causing `npm ci` to fail with exit code 57005 in the aspnetcore build step on Windows legs.

See also https://github.com/nodejs/node/issues/62991