fix(hipsparse): Fix doxygen errors caused by README

[jsandham]

Motivation

Fix Doxygen build failure from unresolved in-page README links

Summary

The documentation build (rocm_docs.doxygen) was aborting with errors like:

README.md:45: error: unable to resolve reference to 'options' for \ref command (warning treated as error, aborting now)
README.md:55: error: unable to resolve reference to 'using-cmake-variables-directly' for \ref command (warning treated as error, aborting now)

Doxygen converts Markdown in-page links ([text](#anchor)) into \ref anchor commands. Unlike GitHub-flavored Markdown, Doxygen does not auto-generate slug anchors from heading text, so these links pointed to non-existent references. Because the docs build treats warnings as errors, this caused Doxygen (and the Sphinx extension wrapping it) to fail.

Changes
Added explicit Doxygen anchors to the headings targeted by in-page links in README.md:

• ## Options → ## Options {#options}

• ### Using CMake variables directly → ### Using CMake variables directly {#using-cmake-variables-directly}

These were the only two ](#...) anchor links in the file.

These errors were not reproducible with doxygen 1.9.1 by are in doxygen 1.9.8

JIRA ID: AISPARSE-590

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[therock-pr-bot]

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