patch 8.1.0950: using :python sets 'pyxversion' even when not executed

Problem:    Using :python sets 'pyxversion' even when not executed.
Solution:   Check the "skip" flag. (Shane Harper, closes #3995)
diff --git a/src/version.c b/src/version.c
index 32abc71..fe498ec 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    950,
+/**/
     949,
 /**/
     948,