[SPARK-27979][BUILD][test-maven] Remove deprecated --force option in build/mvn and run-tests.py

## What changes were proposed in this pull request?

This is a second try of apache#24824.

Since Apache Spark 2.0.0, SPARK-14867 deprecated `--force` option and made it ignored. This PR cleans up the related code completely at 3.0.0.

**BEFORE (Jenkins)**
```
========================================================================
Building Spark
========================================================================
[info] Building Spark using Maven with these arguments:  -Phadoop-2.7 -Pkubernetes -Phive-thriftserver -Pkinesis-asl -Pyarn -Pspark-ganglia-lgpl -Phive -Pmesos clean package -DskipTests
WARNING: '--force' is deprecated and ignored.
...
========================================================================
Running Spark unit tests
========================================================================
[info] Running Spark tests using Maven with these arguments:  -Phadoop-2.7 -Phive-thriftserver -Phive -Dtest.exclude.tags=org.apache.spark.tags.ExtendedHiveTest,org.apache.spark.tags.ExtendedYarnTest test --fail-at-end
WARNING: '--force' is deprecated and ignored.
```

**AFTER (Jenkins)**
```
========================================================================
Building Spark
========================================================================
[info] Building Spark using Maven with these arguments:  -Phadoop-2.7 -Pkubernetes -Phive-thriftserver -Pkinesis-asl -Pyarn -Pspark-ganglia-lgpl -Phive -Pmesos clean package -DskipTests
...
========================================================================
Running Spark unit tests
========================================================================
[info] Running Spark tests using Maven with these arguments:  -Phadoop-2.7 -Pkubernetes -Phive-thriftserver -Pyarn -Pspark-ganglia-lgpl -Phive -Pkinesis-asl -Pmesos -Dtest.exclude.tags=org.apache.spark.tags.ExtendedHiveTest,org.apache.spark.tags.ExtendedYarnTest test --fail-at-end
```

## How was this patch tested?

Manually check the Jenkins logs.

Closes apache#24833 from dongjoon-hyun/SPARK-FORCE-2.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

build/mvn

@@ -134,12 +134,6 @@ install_scala() {
 # the environment
 ZINC_PORT=${ZINC_PORT:-"3030"}
 
-# Remove `--force` for backward compatibility.
-if [ "$1" == "--force" ]; then
-  echo "WARNING: '--force' is deprecated and ignored."
-  shift
-fi
-
 # Install the proper version of Scala, Zinc and Maven for the build
 install_zinc
 install_scala

dev/run-tests.py

@@ -240,7 +240,7 @@ def exec_maven(mvn_args=()):
     zinc_port = get_zinc_port()
     os.environ["ZINC_PORT"] = "%s" % zinc_port
     zinc_flag = "-DzincPort=%s" % zinc_port
-    flags = [os.path.join(SPARK_HOME, "build", "mvn"), "--force", zinc_flag]
+    flags = [os.path.join(SPARK_HOME, "build", "mvn"), zinc_flag]
     run_cmd(flags + mvn_args)