run `pip install nvflare==2.1.2` brings wrong `protobuf` version
When using `pip install nvflare==2.1.2`, protobuf 4.21.4 is installed:
```
Collecting protobuf<5.0.0dev,>=3.15.0
  Downloading protobuf-4.21.4-cp37-abi3-manylinux2014_x86_64.whl (408 kB)
```
and when starting the server (`./poc/server/startup/start.sh`), I got the following error:
```
TypeError: Descriptors cannot not be created directly.
If this call came from a _pb2.py file, your generated code is out of date and must be regenerated with protoc >= 3.19.0.
If you cannot immediately regenerate your protos, some other possible workarounds are:
 1. Downgrade the protobuf package to 3.20.x or lower.
 2. Set PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python (but this will use pure-Python parsing and will be much slower).
```
downgrade into 3.20.1 solves the issue:
```
 pip install protobuf==3.20.1
```
In the `requirements-min.txt` of v2.1.2, it specifies to use `protobuf==3.20.1` (https://github.com/NVIDIA/NVFlare/blob/2.1.2/requirements-min.txt#L7), but why this requirement does not work when running the pip install command? Is there anything wrong here?

diff --git a/setup.py b/setup.py
index 67f509df..58ea808a 100644
--- a/setup.py
+++ b/setup.py
@@ -12,9 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import datetime
 import os
 import shutil
-import datetime
 
 from setuptools import find_packages, setup
 
@@ -73,15 +73,17 @@ setup(
     long_description_content_type="text/markdown",
     python_requires=">=3.7,<3.9",
     install_requires=[
-        "PyYAML",
-        "psutil",
+        "PyYAML==6.0",
+        "psutil==5.9.1",
         "numpy",
-        "grpcio",
-        "google-api-python-client",
+        "grpcio==1.46.3",
+        "protobuf==3.20.1",
+        "google-api-python-client==2.49.0",
         "cryptography>=36.0.0",
+        "Flask==2.1.2",
+        "gunicorn==20.1.0",
+        "six>=1.15.0",
         "tenseal==0.3.0",
-        "gunicorn",
-        "flask",
     ],
     entry_points={
         "console_scripts": [
['setup.py']