chore(python): use debugpy-adapter executable for nvim-dap-python (#6080)

## Description

Uses a less hacky and now officially-supported way of getting the
debugpy DAP adapter path for nvim-dap-python.

Since https://github.com/mfussenegger/nvim-dap-python/pull/184,
nvim-dap-python can start the debugpy adapter using the
`debugpy-adapter` executable. Since
[Mason](f7c1c2fde2/packages/debugpy/package.yaml (L17))
and [now debugpy itself](https://github.com/microsoft/debugpy/pull/1870)
provide this executable, there's no need to get the `python` executable
from debugpy's venv.

I've gone with just `"debugpy-adapter"` rather than
`LazyVim.get_pkg_path("debugpy", "debugpy-adapter")` so that a
system-wide installation of debugpy can also be used.

## Related Issue(s)

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  If this PR fixes any issues, please link to the issue here.
  - Fixes #<issue_number>
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## Screenshots

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## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/plugins/extras/lang/python.lua

@@ -103,11 +103,7 @@ return {
         { "<leader>dPc", function() require('dap-python').test_class() end, desc = "Debug Class", ft = "python" },
       },
       config = function()
-        if vim.fn.has("win32") == 1 then
-          require("dap-python").setup(LazyVim.get_pkg_path("debugpy", "/venv/Scripts/pythonw.exe"))
-        else
-          require("dap-python").setup(LazyVim.get_pkg_path("debugpy", "/venv/bin/python"))
-        end
+        require("dap-python").setup("debugpy-adapter")
       end,
     },
   },