patch 8.2.1128: the write message mentions characters, but it's bytes

Problem:    The write message mentions characters, but it's actually bytes.
Solution:   Change "C" to "B" and "characters" to "bytes".
diff --git a/src/testdir/test_cscope.vim b/src/testdir/test_cscope.vim
index a1a839f..9d12e2f 100644
--- a/src/testdir/test_cscope.vim
+++ b/src/testdir/test_cscope.vim
@@ -103,7 +103,7 @@
     for cmd in ['cs find f Xmemfile_test.c', 'cs find 7 Xmemfile_test.c']
       enew
       let a = execute(cmd)
-      call assert_true(a =~ '"Xmemfile_test.c" \d\+L, \d\+C')
+      call assert_true(a =~ '"Xmemfile_test.c" \d\+L, \d\+B')
       call assert_equal('Xmemfile_test.c', @%)
     endfor
 
@@ -113,7 +113,7 @@
       let a = execute(cmd)
       let alines = split(a, '\n', 1)
       call assert_equal('', alines[0])
-      call assert_true(alines[1] =~ '"Xmemfile_test.c" \d\+L, \d\+C')
+      call assert_true(alines[1] =~ '"Xmemfile_test.c" \d\+L, \d\+B')
       call assert_equal('(1 of 1): <<global>> #include <assert.h>', alines[2])
       call assert_equal('#include <assert.h>', getline('.'))
     endfor