doc: update README after small patch

README.md

@@ -98,16 +98,16 @@ cd arceos
 make clean
 # Example Pattern: make ARCH=<arch>  LOG=<log> A=path/to/app FEATURES=...  run
 # riscv64 example
-make ARCH=riscv64 LOG=debug A=examples/helloworld FEATURES=page-alloc-4g run
+make ARCH=riscv64 LOG=debug A=examples/helloworld run
 # x86_64 example
 make clean
-make ARCH=x86_64 LOG=debug A=examples/helloworld FEATURES=page-alloc-4g run
+make ARCH=x86_64 LOG=debug A=examples/helloworld run
 # aarch64 example
 make clean
-make ARCH=aarch64 LOG=debug A=examples/helloworld FEATURES=page-alloc-4g run
-# loongarch64 example, use 'Ctrl a+x' to quit QEMU
+make ARCH=aarch64 LOG=debug A=examples/helloworld run
+# loongarch64 example
 make clean
-make ARCH=loongarch64 LOG=debug A=examples/helloworld FEATURES=page-alloc-4g run
+make ARCH=loongarch64 LOG=debug A=examples/helloworld run
 ```
 
 Where `path/to/app` is the relative path to the application. Examples applications can be found in the [examples](examples/) directory or the [arceos-apps](https://github.com/arceos-org/arceos-apps) repository.