Updated chromium/.gclient and sync_chromium.py to not ignore third_party/ffmpeg.

Was forgotten in this CL: https://codereview.webrtc.org/1575913003/

BUG=468365
R=kjellander@webrtc.org

Review URL: https://codereview.webrtc.org/1579153003 .

Cr-Commit-Position: refs/heads/master@{#11222}

chromium/.gclient

@@ -10,7 +10,6 @@ solutions = [{
     'src/chrome/tools/test/reference_build/chrome_win': None,
     'src/native_client': None,
     'src/third_party/cld_2/src': None,
-    'src/third_party/ffmpeg': None,
     'src/third_party/hunspell_dictionaries': None,
     'src/third_party/liblouis/src': None,
     'src/third_party/pdfium': None,

sync_chromium.py

@@ -31,7 +31,7 @@ import textwrap
 
 # Bump this whenever the algorithm changes and you need bots/devs to re-sync,
 # ignoring the .last_sync_chromium file
-SCRIPT_VERSION = 6
+SCRIPT_VERSION = 7
 
 ROOT_DIR = os.path.dirname(os.path.abspath(__file__))
 CHROMIUM_NO_HISTORY = 'CHROMIUM_NO_HISTORY'