Printing: Remove old field trials

Remove field trial configs for print scaling and print PDF as image,
since these features have launched.

Bug: None
Change-Id: I667a797ebc4bdbe71fe37acf4a00ef0d34718223
Reviewed-on: https://chromium-review.googlesource.com/1103307Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568465}

testing/variations/fieldtrial_testing_config.json

@@ -2976,40 +2976,6 @@
             ]
         }
     ],
-    "PrintPdfAsImage": [
-        {
-            "platforms": [
-                "chromeos",
-                "linux"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "PrintPdfAsImage"
-                    ]
-                }
-            ]
-        }
-    ],
-    "PrintScaling": [
-        {
-            "platforms": [
-                "chromeos",
-                "linux",
-                "mac",
-                "win"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "PrintScaling"
-                    ]
-                }
-            ]
-        }
-    ],
     "PrioritizedSimpleCacheTasks": [
         {
             "platforms": [