Add change note for buffered i/o

Author: Sauyon Lee

change-notes/1.24/extractor-go.md

@@ -10,6 +10,7 @@
 * The autobuilder now runs Makefiles or custom build scripts present in the codebase to install dependencies. The build command
   to invoke can be configured via `lgtm.yml`, or by setting the environment variable `CODEQL_EXTRACTOR_GO_BUILD_COMMAND`.
 * The autobuilder now attempts to automatically detect when dependencies have been vendored and use `-mod=vendor` appropriately.
+* The extractor now uses buffered i/o for writing database files, which reduces the amount of time taken for extraction.
 * The extractor now compresses intermediate files used for constructing databases, which reduces the amount of disk space it requires.
 * The extractor now supports extracting go.mod files, enabling queries on dependencies and their versions.
 * The extractor now supports Go 1.14.