editor: vscode: do not trim diff file trailing whitespace

This rule will break the patch structure.

Fixes: af75e1c527 ("vscode: update editor formatting and line endings settings")
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/24411
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>

.vscode/settings.json

@@ -3,5 +3,9 @@
     "files.trimTrailingWhitespace": true,
     "files.insertFinalNewline": true,
     "files.trimFinalNewlines": true,
-    "files.eol": "\n"
+    "files.eol": "\n",
+
+    "[diff]": {
+        "files.trimTrailingWhitespace": false
+    }
 }