Removed Experimental tag from representaives

With recent changes the flaky stories are prevented by invalidating failures using cpu_wall_time_ratio (https://chromium-review.googlesource.com/c/chromium/src/+/2292811), the previously flaky stories do not need to stay marked as experimental.

Bug: 1053614,1093313
Change-Id: I64120d9ba34a2363f21a943131b66d65f20e301f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332737Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Behdad Bakhshinategh <behdadb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793678}

testing/scripts/representative_perf_test_data/representatives_frame_times_upper_limit.json

@@ -7,10 +7,8 @@
     },
     "filter_terrain_svg": {
       "ci_095": 0.574,
-      "_comment": "crbug.com/1053614",
       "avg": 33.202,
-      "cpu_wall_time_ratio": 0.368,
-      "experimental": true
+      "cpu_wall_time_ratio": 0.368
     },
     "web_animation_value_type_transform_complex": {
       "ci_095": 1.704,
@@ -70,10 +68,8 @@
     },
     "css_value_type_shadow": {
       "ci_095": 1.482,
-      "_comment": "crbug.com/1093313",
       "avg": 56.704,
-      "cpu_wall_time_ratio": 0.414,
-      "experimental": true
+      "cpu_wall_time_ratio": 0.414
     },
     "nvidia_vertex_buffer_object": {
       "ci_095": 3.605,
@@ -109,10 +105,8 @@
     },
     "css_value_type_shadow": {
       "ci_095": 18.3,
-      "_comment": "crbug.com/1093313",
       "avg": 65.502,
-      "cpu_wall_time_ratio": 0.585,
-      "experimental": true
+      "cpu_wall_time_ratio": 0.585
     },
     "animometer_webgl_attrib_arrays": {
       "ci_095": 0.44,