fix typo in iOS pipeline (#22067)

### Description
<!-- Describe your changes. -->



### Motivation and Context
The parameter isn't correct.
Maybe it hasn't negative impact by chance so far.

https://github.com/microsoft/onnxruntime/blob/d8e64bb529c1d0f18efd47710d179205c96ffbca/cmake/CMakeLists.txt#L1712-L1717

tools/ci_build/github/azure-pipelines/mac-ios-ci-pipeline.yml

@@ -53,7 +53,7 @@ jobs:
               python3 $(Build.SourcesDirectory)/tools/ci_build/build.py \
                 --skip_submodule_sync \
                 --build_dir $(Build.BinariesDirectory)/iOS \
-                --build_shared \
+                --build_shared_lib \
                 --use_coreml \
                 --use_xnnpack \
                 --ios \