metrics: remove unused constant

A constant was left during the refactoring
(https://chromium-review.googlesource.com/#/c/207237/) and it is failing the
generic ASAN buildbot.

BUG=chromium:374368
TEST=FEATURES=test emerge-amd64-generic metrics

Change-Id: Ief9f2a064dbeded87e2e5fc67d3659fedac88867
Reviewed-on: https://chromium-review.googlesource.com/207460
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
diff --git a/metrics/metrics_library.cc b/metrics/metrics_library.cc
index c418864..ac97c3e 100644
--- a/metrics/metrics_library.cc
+++ b/metrics/metrics_library.cc
@@ -23,7 +23,6 @@
 static const char kAutotestPath[] = "/var/log/metrics/autotest-events";
 static const char kUMAEventsPath[] = "/var/run/metrics/uma-events";
 static const char kConsentFile[] = "/home/chronos/Consent To Send Stats";
-static const int32_t kBufferSize = 1024;
 static const char kCrosEventHistogramName[] = "Platform.CrOSEvent";
 static const int kCrosEventHistogramMax = 100;