Fix buggy md syntax in technical-overview.md (#221)

## Ticket

Resolves linter complaint:
```
  ERROR: 1 dead links found!
  [✖] alembic-src → Status: 400
```

## Changes

Use square brackets, not parentheses.

## Context for reviewers

> Testing instructions, background context, more in-depth details of the
implementation, and anything else you'd like to call out or ask
reviewers.

## Testing

The markdown linter should not cause this error.

docs/app/technical-overview.md

@@ -19,7 +19,7 @@ generally preferred.
 - [OpenAPI Specification][oas-docs]
 - [API Flask][apiflask-home] ([source code][apiflask-src])
 - [SQLAlchemy][sqlalchemy-home] ([source code][sqlalchemy-src])
-- [Alembic][alembic-home] ([source code](alembic-src))
+- [Alembic][alembic-home] ([source code][alembic-src])
 - [pydantic][pydantic-home] ([source code][pydantic-src])
 - [poetry](https://python-poetry.org/docs/) - Python dependency management
 
@@ -57,4 +57,4 @@ function that is run to do the authentication.
 n/a - Specific user authorization is not yet implemented for this API.
 
 ### Database diagram
-n/a - Database diagrams are not yet available for this application.
+n/a - Database diagrams are not yet available for this application.