patch 8.2.0481: Travis is still using trusty

Problem:    Travis is still using trusty.
Solution:   Adjust config to use bionic. (Ozaki Kiichi, closes #5868)

src/testdir/lsan-suppress.txt

@@ -1,3 +1,11 @@
-# Suppress leaks from X libraries on Ubuntu trusty.
+# Suppress leaks from X libraries on Ubuntu bionic.
 leak:libX11.so.6
 leak:libXt.so.6
+leak:libcairo.so.2
+leak:libfontconfig.so.1
+leak:libglib-2.0.so.0
+leak:libtinfo.so.5
+# Suppress leaks from other language libraries.
+leak:libperl.so.*
+leak:libpython*.so.*
+leak:libruby*.so.*

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    481,
 /**/
     480,
 /**/