fix: remove dependency on workspace_root

[rgrinberg]

It wa only used in one particular case where we need a location for a
diagnostic and doesn't give us one.

Instead, we use the dune instance's directory as the location.

Signed-off-by: Rudi Grinberg me@rgrinberg.com

[coveralls]

Pull Request Test Coverage Report for Build 3844

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 3 (0.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.002%) to 17.351%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ocaml-lsp-server/src/dune.ml	0	3	0.0%

Files with Coverage Reduction	New Missed Lines	%
ocaml-lsp-server/src/import.ml	1	35.9%
ocaml-lsp-server/src/ocaml_lsp_server.ml	1	36.47%

Totals
Change from base Build 3838:	-0.002%
Covered Lines:	4072
Relevant Lines:	23469

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💛 - Coveralls