Simplify whitespace purge script a little.

Do not need to test with -f. If directories ever show up in git
ls-files (unlikely) their mime type is application/x-directory which
will fail the test ${file::4} == text check.

Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>

contrib/whitespace-purge.sh

@@ -17,7 +17,7 @@ for file in $(git ls-files) ; do
     # skip sym links, pdfs, etc. If any other file types should be
     # skipped add the check here.
     type=$(file -b --mime-type -h $file)
-    if test -f $file && test ${type::4} == "text" ; then
+    if test ${type::4} == "text" ; then
         LC_ALL=C sed -i '' -E "s/[[:space:]]*$//" $file
     fi
 done