Remove obsolete LIB/INCLUDE workaround from Windows conda build script

[antonwolfy]

Removes a stale workaround from conda-recipe/bld.bat that manually prepended BUILD_PREFIX paths onto the Windows LIB and INCLUDE environment variables.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/pull/3013/index.html

[github-actions]

Array API standard conformance tests for dpnp=0.21.0dev3=py314h509198e_36 ran successfully.
Passed: 1375
Failed: 2
Skipped: 5

[coveralls]

coverage: 78.414%. remained the same — remove-compiler-w/a-to-dpnp-bld.bat into master

[ndgrigorian]

LGTM