fix(django-spanner): declare django dependency in setup.py (#18044)

## Description
Declares `"django >= 5.2, < 5.3"` in `install_requires` (`dependencies`)
for `django-google-spanner`.

## Motivation
`django_spanner` imports and requires `django` directly at top-level
import time and explicitly checks for Django 5.2 compatibility in
`django_spanner/__init__.py`.

Without `django` listed in `setup.py`, installing
`django-google-spanner` in a clean environment (such as during the
`import-profiler` presubmit check) caused imports to fail with:
ModuleNotFoundError: No module named 'django'

Tracking issue for Django 6.0 support: #18053

Author: hebaalazzeh

packages/django-google-spanner/setup.py

@@ -18,7 +18,13 @@
 # 'Development Status :: 4 - Beta'
 # 'Development Status :: 5 - Production/Stable'
 release_status = "Development Status :: 5 - Production/Stable"
-dependencies = ["sqlparse >= 0.3.0", "google-cloud-spanner >= 3.13.0"]
+# TODO(https://github.com/googleapis/google-cloud-python/issues/18053): Update upper bound when adding support for Django 6.0+
+# (django_spanner/__init__.py currently enforces SUPPORTED_DJANGO_VERSIONS = [(5, 2)])
+dependencies = [
+    "sqlparse >= 0.3.0",
+    "google-cloud-spanner >= 3.13.0",
+    "django >= 5.2, < 6.0",
+]
 extras = {
     "tracing": [
         "opentelemetry-api >= 1.1.0",