[SPARK-24263][R] SparkR java check breaks with openjdk

## What changes were proposed in this pull request?

Change text to grep for.

## How was this patch tested?

manual test

Author: Felix Cheung <[email protected]>

Closes apache#21314 from felixcheung/openjdkver.

Author: felixcheung

R/pkg/R/client.R

@@ -82,7 +82,7 @@ checkJavaVersion <- function() {
                    })
   javaVersionFilter <- Filter(
       function(x) {
-        grepl("java version", x)
+        grepl(" version", x)
       }, javaVersionOut)
 
   javaVersionStr <- strsplit(javaVersionFilter[[1]], "[\"]")[[1L]][2]