Replace python-ldap with openldap in conda env

On PyPI, `python-ldap` is distributed as an *sdist* only, not *wheel*.
But it still requires a compilation step before installation.

Some dependencies installed with conda are rightfully ignored by Poetry.
Even when `python-ldap` is pre-installed by conda,
Poetry would still need to reinstall it which implies compilation.
Indeed there is an issue in how conda packages are created
and how they are installed:
* <python-poetry/poetry#6408 (comment)>
* <conda-forge/python-ldap-feedstock#28>

So it does not make much sense to let conda install `python-ldap`.
Instead we can instruct conda to install `openldap` only,
and pip and Poetry should be able to compile `python-ldap`.

GitHub: mxcube/mxcubeweb#1510
GitHub: #849 (comment)
GitHub: conda-forge/python-ldap-feedstock#28
GitHub: #851

conda-environment-dev.yml

@@ -2,24 +2,28 @@
 ---
 
 name: mxcubecore
+
 channels:
   - conda-forge
+
 dependencies:
 
-  ### Runtime dependencies
+  # Runtime dependencies
+  # ====================
 
   - python >=3.8,<3.12
 
-  # We install `python-ldap` from conda because it is "hard" to install.
-  # On PyPI it is not available as *wheel*, only as *sdist* which requires to be built
-  # with compilation steps that require a compiler and some header files.
-  # Installing with conda is much "easier".
-  #
-  # IMPORTANT:
-  # Always make sure that `python-ldap` here is pinned to the same version
-  # as in the Poetry lockfile `poetry.lock` (not the other way around).
-  - python-ldap=3.4.3
-
-  ### Development dependencies
+  # `openldap` is necessary for `python-ldap` but can not be installed by pip or Poetry.
+  # Note also that on PyPI `python-ldap` is only available as *sdist*, not as *wheel*,
+  # and that installing it requires a compilation step.
+  # The `openldap` Conda package should provide enough for this compilation step
+  # (header files and things like this), but the C compiler itself.
+  # Make sure that a C compiler is available on the system,
+  # as it is NOT provided as a dependency in this Conda environment file.
+  - openldap
+
+
+  # Development dependencies
+  # ========================
 
   - poetry