Fixed duplicate "stripInternal" entry in client-sts tsconfig

This caused an error for me when bundling with esbuild
> node_modules/@aws-sdk/client-ecs/node_modules/@aws-sdk/client-sts/tsconfig.json:26:4: warning: Duplicate key "stripInternal" in object literal
    26 │     "stripInternal": true,
       ╵     ~~~~~~~~~~~~~~~

Author: aaroncowie

clients/client-sts/tsconfig.json

@@ -23,7 +23,6 @@
     "ignoreCompilerErrors": true,
     "includeDeclarations": true,
     "stripInternal": true,
-    "stripInternal": true,
     "readme": "./README.md",
     "mode": "file",
     "out": "./docs",