patch 8.2.3325: digraph test fails when LC_ALL is set to "C"

Problem:    Digraph test fails when LC_ALL is set to "C".
Solution:   When restoring 'encoding' set it to "utf-8". (closes #8742)

src/testdir/test_digraph.vim

@@ -557,6 +557,7 @@ endfunc
 
 func Test_digraph_get_function_encode()
   CheckFeature iconv
+
   let testcases = {
         \'00': '∞',
         \'aa': 'あ',
@@ -565,7 +566,7 @@ func Test_digraph_get_function_encode()
     call digraph_set(key, ch)
     set encoding=japan
     call assert_equal(iconv(ch, 'utf-8', 'japan'), digraph_get(key))
-    set encoding&
+    set encoding=utf-8
   endfor
 endfunc
 
@@ -592,4 +593,6 @@ func Test_digraph_getlist_function()
   call assert_equal(digraph_getlist()->len(), digraph_getlist(0)->len())
   call assert_notequal((digraph_getlist()->len()), digraph_getlist(1)->len())
 endfunc
+
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3325,
 /**/
     3324,
 /**/