Prepare for a release compatible with 4.14

[voodoos]

4.14.x is still considered an "LTS" version and Merlin continued releasing new features and fixes that have not been available to ocaml-lsp users. This PR rolls back changes specific to later version of OCaml so that we can release a new version of ocaml-lsp compatible with 4.14.

It should not be merged on master but on a new dedicated branch.

[coveralls]

Pull Request Test Coverage Report for Build 4628

Details

• 44 of 72 (61.11%) changed or added relevant lines in 11 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.07%) to 22.199%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ocaml-lsp-server/src/code_actions/action_add_rec.ml	0	1	0.0%
ocaml-lsp-server/src/code_actions/action_mark_remove_unused.ml	1	2	50.0%
ocaml-lsp-server/src/document_symbol.ml	0	1	0.0%
ocaml-lsp-server/src/rename.ml	0	1	0.0%
ocaml-lsp-server/src/workspace_symbol.ml	0	1	0.0%
ocaml-lsp-server/src/code_actions/action_inline.ml	39	41	95.12%
ocaml-lsp-server/src/hover_req.ml	0	2	0.0%
ocaml-lsp-server/src/ocaml_lsp_server.ml	0	2	0.0%
ocaml-lsp-server/src/folding_range.ml	0	5	0.0%
ocaml-lsp-server/src/semantic_highlighting.ml	3	15	20.0%

Files with Coverage Reduction	New Missed Lines	%
ocaml-lsp-server/src/semantic_highlighting.ml	1	51.35%
ocaml-lsp-server/src/ocaml_lsp_server.ml	2	38.04%

Totals
Change from base Build 4625:	0.07%
Covered Lines:	5652
Relevant Lines:	25461

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💛 - Coveralls