Remove pinning of grpcio dependencies (#485)

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**What this PR does / why we need it**:
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the problem you're trying to solve. --->

With #465, we no longer need to
pin the `grpcio` related libraries, which will in turn constrain the
`protobuf` dependencies.

**Which issue(s) this PR fixes**:
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Fixes #

**Does this PR introduce a user-facing change?**:
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```release-note
Remove pinning of grpcio dependencies
```

**Checklist**

- [ ] Added unit test, integration, and/or e2e tests
- [ ] Tested locally
- [ ] Updated documentation
- [ ] Update Swagger spec if the PR introduce API changes
- [ ] Regenerated Golang and Python client if the PR introduce API
changes

examples/custom-model/upi_v1/requirements.txt

@@ -1,4 +1,3 @@
 merlin-sdk
-grpcio>=1.31.0,<1.49.0
 caraml-upi-protos>=0.3.1
 pandas

examples/transformer/upi/requirements.txt

@@ -1,4 +1,3 @@
 pandas
 cloudpickle==2.0.0
-merlin-sdk
-grpcio==1.22.0
+merlin-sdk

python/batch-predictor/main.py

@@ -122,7 +122,7 @@ def main(spec_path, spark):
             .builder \
             .appName(args.job_name) \
             .getOrCreate()
-        spark.conf.set("spark.sql.execution.arrow.enabled", "true")
+        spark.conf.set("spark.sql.execution.arrow.pyspark.enabled", "true")
 
     print(f"Spark Conf: {spark.sparkContext.getConf().getAll()}")
     if args.dry_run_path is not None:

python/batch-predictor/requirements.txt

@@ -3,5 +3,4 @@ pyspark==3.0.1
 mlflow>=1.26.1,<2.0.0
 cloudpickle==2.0.0
 pyarrow>=0.14.1,<=9.0.0
-protobuf>=3.0,<5.0.0
 file:${SDK_PATH}#egg=merlin-sdk

python/pyfunc-server/requirements.txt

@@ -7,9 +7,4 @@ uvloop>=0.15.2,<0.18.0
 orjson>=2.6.8
 tornado
 caraml-upi-protos
-# Starting 1.49.0, grpc uses protobuf 4.X which are incompatible with most of our dependencies
-grpcio<1.49.0
-grpcio-reflection<1.49.0
-grpcio-tools<1.49.0
-grpcio-health-checking<1.49.0
 file:${SDK_PATH}#egg=merlin-sdk

python/sdk/setup.py

@@ -44,7 +44,6 @@
 TEST_REQUIRES = [
     "google-cloud-bigquery-storage>=0.7.0",
     "google-cloud-bigquery>=1.18.0",
-    "grpcio>=1.31.0,<1.49.0",
     "joblib>=0.13.0,<1.2.0",  # >=1.2.0 upon upgrade of kserve's version
     "mypy>=0.812",
     "pytest-cov",