[SPARK-32491][INFRA] Do not install SparkR in test-only mode in testing script

This PR proposes to skip SparkR installation that is to run R linters (see SPARK-8505) in the test-only mode at `dev/run-tests.py` script.

As of SPARK-32292, the test-only mode in `dev/run-tests.py` was introduced, for example:

```
dev/run-tests.py --modules sql,core
```

which only runs the relevant tests and does not run other tests such as linters. Therefore, we don't need to install SparkR when `--modules` are specified.

GitHub Actions build is currently failed as below:

```
ERROR: this R is version 3.4.4, package 'SparkR' requires R >= 3.5
[error] running /home/runner/work/spark/spark/R/install-dev.sh ; received return code 1
```

For some reasons, looks GitHub Actions started to have R 3.4.4 installed by default; however, R 3.4 was dropped as of SPARK-32073.  When SparkR tests are not needed, GitHub Actions still builds SparkR with a low R version and it causes the test failure.

This PR partially fixes it by avoid the installation of SparkR.

No, dev-only.

GitHub Actions tests should run to confirm this fix is correct.

Closes apache#29300 from HyukjinKwon/install-r.

Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

Author: HyukjinKwon

dev/run-tests.py

@@ -556,13 +556,14 @@ def main():
               " install one and retry.")
         sys.exit(2)
 
-    java_version = determine_java_version(java_exe)
-
-    # install SparkR
-    if which("R"):
-        run_cmd([os.path.join(SPARK_HOME, "R", "install-dev.sh")])
-    else:
-        print("Cannot install SparkR as R was not found in PATH")
+    # Install SparkR
+    should_only_test_modules = opts.modules is not None
+    if not should_only_test_modules:
+        # If tests modules are specified, we will not run R linter.
+        if which("R"):
+            run_cmd([os.path.join(SPARK_HOME, "R", "install-dev.sh")])
+        else:
+            print("Cannot install SparkR as R was not found in PATH")
 
     if os.environ.get("AMPLAB_JENKINS"):
         # if we're on the Amplab Jenkins build servers setup variables
@@ -587,7 +588,6 @@ def main():
     changed_modules = None
     test_modules = None
     changed_files = None
-    should_only_test_modules = opts.modules is not None
     included_tags = []
     excluded_tags = []
     if should_only_test_modules: