build: bump symbolic to 2.0.7 (#7319)

requirements-base.txt

@@ -50,7 +50,7 @@ statsd>=3.1.0,<3.2.0
 strict-rfc3339>=0.7
 structlog==16.1.0
 sqlparse>=0.1.16,<0.2.0
-symbolic>=2.0.4,<3.0.0
+symbolic>=2.0.7,<3.0.0
 toronado>=0.0.11,<0.1.0
 ua-parser>=0.6.1,<0.8.0
 urllib3>=1.22,<1.23