Bump lmdb from 0.97 to 1.2.1 (#754)

Bumps [lmdb](https://github.com/jnwatson/py-lmdb) from 0.97 to 1.2.1.
- [Release notes](https://github.com/jnwatson/py-lmdb/releases)
- [Changelog](https://github.com/jnwatson/py-lmdb/blob/master/ChangeLog)
- [Commits](jnwatson/py-lmdb@py-lmdb_0.97...py-lmdb_1.2.1)

Signed-off-by: dependabot[bot] <[email protected]>

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==0.97; sys_platform != 'win32'
+lmdb==1.2.1; sys_platform != 'win32'
 # optional library requirements for Jupyter
 ipytree==0.2.1
 # optional library requirements for services