Roll external/abseil_cpp/ 820cd9ee9..b9baf19a1 (97 commits)

abseil/abseil-cpp@820cd9e...b9baf19

Created with:
  roll-dep external/abseil_cpp

Author: GitHub Actions[bot]

DEPS

@@ -3,7 +3,7 @@ use_relative_paths = True
 vars = {
   'github': 'https://github.com',
 
-  'abseil_revision': '820cd9ee904158c1395d4198bd568145715537aa',
+  'abseil_revision': 'b9baf19a19821c22725f6fa7eedc107e47c33e5f',
 
   'effcee_revision': '514b52ec61609744d7e587d93a7ef9b60407ab45',