Fix minor styling issue in resolve_variables

Co-authored-by: bruntib <12861163+bruntib@users.noreply.github.com>

Author: barnabasdomozi

web/server/codechecker_server/session_manager.py

@@ -444,7 +444,7 @@ def resolve_variables(d):
                         if secret_matched and var_name in secrets_dict:
                             d[k] = secrets_dict[var_name]
                         elif env_matched and var_name in os.environ:
-                            d[k] = os.environ.get(var_name)
+                            d[k] = os.environ[var_name]
                         else:
                             resolve_variables_failed(v)