patch 9.0.1422: Sage files are not recognized

Problem:    Sage files are not recognized.
Solution:   Add a pattern for Sage files. (Amaan Qureshi, closes #12176)
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 55548e4..e5f16cd 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -540,6 +540,7 @@
     \ 'skill': ['file.il', 'file.ils', 'file.cdf'],
     \ 'cdc': ['file.cdc'],
     \ 'slang': ['file.sl'],
+    \ 'sage': ['file.sage'],
     \ 'slice': ['file.ice'],
     \ 'slpconf': ['/etc/slp.conf', 'any/etc/slp.conf'],
     \ 'slpreg': ['/etc/slp.reg', 'any/etc/slp.reg'],
diff --git a/src/version.c b/src/version.c
index f6cac46..8ed8263 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1422,
+/**/
     1421,
 /**/
     1420,