patch 8.2.4190: all conceal tests are skipped without the screendumps feature

Problem:    All conceal tests are skipped without the screendumps feature.
Solution:   Only skip the tests that use screendumps. (closes #9599)

src/testdir/test_conceal.vim

@@ -4,9 +4,10 @@ source check.vim
 CheckFeature conceal
 
 source screendump.vim
-CheckScreendump
 
 func Test_conceal_two_windows()
+  CheckScreendump
+
   let code =<< trim [CODE]
     let lines = ["one one one one one", "two |hidden| here", "three |hidden| three"]
     call setline(1, lines)
@@ -111,6 +112,8 @@ func Test_conceal_two_windows()
 endfunc
 
 func Test_conceal_with_cursorline()
+  CheckScreendump
+
   " Opens a help window, where 'conceal' is set, switches to the other window
   " where 'cursorline' needs to be updated when the cursor moves.
   let code =<< trim [CODE]
@@ -138,6 +141,8 @@ func Test_conceal_with_cursorline()
 endfunc
 
 func Test_conceal_resize_term()
+  CheckScreendump
+
   let code =<< trim [CODE]
     call setline(1, '`one` `two` `three` `four` `five`, the backticks should be concealed')
     setl cocu=n cole=3

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4190,
 /**/
     4189,
 /**/