Fix dependencies of standard provider (#43553)

Standard provider should have virtualenv as dependency set as it
has PythonVirtualenvOperator that needs it. Also it should have
min airflow version 2.8.0 same as all other providers.

Author: potiuk

generated/provider_dependencies.json

@@ -1286,7 +1286,8 @@
   "standard": {
     "deps": [
       "apache-airflow-providers-common-sql>=1.18.0",
-      "apache-airflow>=2.10.0"
+      "apache-airflow>=2.8.0",
+      "virtualenv>=20.26.0"
     ],
     "devel-deps": [],
     "plugins": [],

providers/src/airflow/providers/standard/provider.yaml

@@ -28,8 +28,9 @@ versions:
   - 1.0.0
 
 dependencies:
-  - apache-airflow>=2.10.0
+  - apache-airflow>=2.8.0
   - apache-airflow-providers-common-sql>=1.18.0
+  - virtualenv>=20.26.0
 
 integrations:
   - integration-name: Standard