WebRtcHybridAgc experiment: update fieldtrial_testing_config.json

Add SSE2 and NEON allowed flags.

Bug: chromium:873650
Change-Id: Ide3a8d64bf16a455a89682cba70398378bde1588
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2662997
Reviewed-by: Olga Sharonova <olka@chromium.org>
Commit-Queue: Ale Bzk <alessiob@chromium.org>
Cr-Commit-Position: refs/heads/master@{#849085}

testing/variations/fieldtrial_testing_config.json

@@ -7696,6 +7696,8 @@
                         "level_estimator_speech_frames_threshold": "6",
                         "max_gain_change_db_per_second": "3",
                         "max_output_noise_level_dbfs": "-55",
+                        "neon_allowed": "true",
+                        "sse2_allowed": "true",
                         "use_peaks_not_rms": "false",
                         "vad_probability_attack": "0.3"
                     },