[SPARK-19232][SPARKR] Update Spark distribution download cache location on Windows

## What changes were proposed in this pull request?

Windows seems to be the only place with appauthor in the path, for which we should say "Apache" (and case sensitive)
Current path of `AppData\Local\spark\spark\Cache` is a bit odd.

## How was this patch tested?

manual.

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16590 from felixcheung/rcachedir.

(cherry picked from commit a115a54)
Signed-off-by: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Author: felixcheung

R/pkg/R/install.R

@@ -50,7 +50,7 @@
 #'                 \itemize{
 #'                   \item Mac OS X: \file{~/Library/Caches/spark}
 #'                   \item Unix: \env{$XDG_CACHE_HOME} if defined, otherwise \file{~/.cache/spark}
-#'                   \item Windows: \file{\%LOCALAPPDATA\%\\spark\\spark\\Cache}.
+#'                   \item Windows: \file{\%LOCALAPPDATA\%\\Apache\\Spark\\Cache}.
 #'                 }
 #' @param overwrite If \code{TRUE}, download and overwrite the existing tar file in localDir
 #'                  and force re-install Spark (in case the local directory or file is corrupted)
@@ -239,7 +239,7 @@ sparkCachePath <- function() {
                    "or restart and enter an installation path in localDir.")
       stop(msg)
     } else {
-      path <- file.path(winAppPath, "spark", "spark", "Cache")
+      path <- file.path(winAppPath, "Apache", "Spark", "Cache")
     }
   } else if (.Platform$OS.type == "unix") {
     if (Sys.info()["sysname"] == "Darwin") {