Integrated: Fix incorrect links in UsingTools.md

[Leonid Kuskov]

Fix incorrect link and header in UsingTools.md

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Commit messages:
 - Fix incorrect links in UsingTools.md

Changes: https://git.openjdk.org/asmtools/pull/95/files
  Webrev: https://webrevs.openjdk.org/?repo=asmtools&pr=95&range=00
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/asmtools/pull/95.diff
  Fetch: git fetch https://git.openjdk.org/asmtools.git pull/95/head:pull/95

PR: https://git.openjdk.org/asmtools/pull/95