Remove remaining quality-analysis (QM).

This was never turned on, contains a lot of complexity and somehow
manages triggering a bug in a downstream project.

BUG=webrtc:5066
R=marpan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1917323002 .

Cr-Commit-Position: refs/heads/master@{#12692}

webrtc/modules/video_processing/video_processing.gypi

@@ -20,8 +20,6 @@
       'sources': [
         'include/video_processing.h',
         'include/video_processing_defines.h',
-        'content_analysis.cc',
-        'content_analysis.h',
         'frame_preprocessor.cc',
         'frame_preprocessor.h',
         'spatial_resampler.cc',
@@ -58,7 +56,6 @@
           'target_name': 'video_processing_sse2',
           'type': 'static_library',
           'sources': [
-            'content_analysis_sse2.cc',
             'util/denoiser_filter_sse2.cc',
             'util/denoiser_filter_sse2.h',
           ],