Remove support for CLI v2.20.4

Author: nickrolfe

extensions/ql-vscode/src/codeql-cli/cli.ts

@@ -45,7 +45,7 @@ import type { LanguageClient } from "vscode-languageclient/node";
  * The oldest version of the CLI that we support. This is used to determine
  * whether to show a warning about the CLI being too old on startup.
  */
-export const OLDEST_SUPPORTED_CLI_VERSION = new SemVer("2.20.7");
+export const OLDEST_SUPPORTED_CLI_VERSION = new SemVer("2.21.4");
 
 /**
  * The version of the SARIF format that we are using.

extensions/ql-vscode/supported_cli_versions.json

@@ -3,6 +3,5 @@
   "v2.23.9",
   "v2.22.4",
   "v2.21.4",
-  "v2.20.7",
   "nightly"
 ]