Deprecate `BraveAds.EpsilonGreedyBanditStudy` griffin study

[tmancey]

        {
            "name": "BraveAds.EpsilonGreedyBanditStudy",
            "experiments": [
                {
                    "name": "Treatment",
                    "probability_weight": 10,
                    "feature_association": {
                        "enable_feature": ["EpsilonGreedyBandit"],
                        "disable_feature": ["TextClassification"]
                    },
                    "parameters": [
                      {
                        "name": "epsilon_value",
                        "value": "0.33"
                      }
                    ]
                },
                {
                    "name": "Control",
                    "probability_weight": 10
                },
                {
                    "name": "Default",
                    "probability_weight": 80
                }
            ],
            "filter": {
                "channel": ["RELEASE","BETA", "NIGHTLY"],
                "platform": ["WINDOWS", "MAC", "LINUX", "ANDROID"],
                "country": ["GB"]
            }
        },

[tmancey]

Before deprecating studies where the feature is enabled by default we should ensure that all users, especially Android users, have proper feature values in the code across all platforms. If the feature is disabled by default then we should test that the default values are working as expected

[tmancey]

Agreed with @ptjames that this study can be removed, thanks