Remove support for CodeQL CLI versions older than v2.18.4

Author: charisk

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

@@ -1904,7 +1904,7 @@ function shouldDebugCliServer() {
 export class CliVersionConstraint {
   // 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.
-  public static OLDEST_SUPPORTED_CLI_VERSION = new SemVer("2.16.6");
+  public static OLDEST_SUPPORTED_CLI_VERSION = new SemVer("2.18.4");
 
   constructor(private readonly cli: CodeQLCliServer) {
     /**/

extensions/ql-vscode/supported_cli_versions.json

@@ -3,7 +3,5 @@
   "v2.19.4",
   "v2.19.3",
   "v2.18.4",
-  "v2.17.6",
-  "v2.16.6",
   "nightly"
 ]