Fix compatibility with Pydantic dropping 3.8 (#804)

Pydantic dropped support for Python 3.9 (and will be effective when 2.11 is released). Because the Logfire SDK still supports 3.8 and as we pin Pydantic to the main branch in our dev dependencies, we need to add a conditional based on the python version.

Author: Viicos

.github/workflows/daily_deps_test.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
         pydantic-version: ['main']
         include:
           - python-version: '3.12'

pyproject.toml

@@ -101,7 +101,8 @@ dev = [
     "pytest >= 8.3.4",
     "pytest-django >= 4.6.0",
     "pytest-pretty >= 1.2.0",
-    "pydantic @ git+https://github.com/pydantic/pydantic",
+    "pydantic @ git+https://github.com/pydantic/pydantic ; python_version >= '3.9'",
+    "pydantic==2.10.5; python_version < '3.9'",
     "requests >= 2.31.0",
     "sqlalchemy >= 1.4.54",
     "pandas>=2.1.2; python_version >= '3.9'",