Update alembic requirement from ~=1.7.7 to ~=1.8.1 in /api

Updates the requirements on [alembic](https://github.com/sqlalchemy/alembic) to permit the latest version.
- [Release notes](https://github.com/sqlalchemy/alembic/releases)
- [Changelog](https://github.com/sqlalchemy/alembic/blob/main/CHANGES)
- [Commits](https://github.com/sqlalchemy/alembic/commits)

---
updated-dependencies:
- dependency-name: alembic
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

api/requirements.txt

@@ -11,4 +11,4 @@ sqlparse~=0.4.2
 sqlalchemy[asyncio]~=1.4.39
 asyncpg~=0.24.0
 pyshp~=2.3.1
-alembic~=1.7.7
+alembic~=1.8.1

api/setup.py

@@ -23,7 +23,7 @@ setup(
         "pyshp>=2.2,<2.4",
         "sqlalchemy[asyncio]~=1.4.25",
         "asyncpg~=0.24.0",
-        "alembic~=1.7.7",
+        "alembic>=1.7.7,<1.9.0",
     ],
     entry_points={
         "console_scripts": [