Bump lmdb from 1.3.0 to 1.4.0 (#1288)

Bumps [lmdb](https://github.com/jnwatson/py-lmdb) from 1.3.0 to 1.4.0.
- [Release notes](https://github.com/jnwatson/py-lmdb/releases)
- [Changelog](https://github.com/jnwatson/py-lmdb/blob/py-lmdb_1.4.0/ChangeLog)
- [Commits](jnwatson/py-lmdb@py-lmdb_1.3.0...py-lmdb_1.4.0)

---
updated-dependencies:
- dependency-name: lmdb
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_dev_optional.txt

@@ -1,6 +1,6 @@
 # optional library requirements
 # bsddb3==6.2.6; sys_platform != 'win32'
-lmdb==1.3.0; sys_platform != 'win32'
+lmdb==1.4.0; sys_platform != 'win32'
 # optional library requirements for Jupyter
 ipytree==0.2.2
 ipywidgets==8.0.3