patch 8.1.1955: tests contain typos

Problem:    Tests contain typos.
Solution:   Correct the typos. (Dominique Pelle)
diff --git a/src/testdir/test49.vim b/src/testdir/test49.vim
index 7393ec4..bd60514 100644
--- a/src/testdir/test49.vim
+++ b/src/testdir/test49.vim
@@ -521,7 +521,7 @@
 "
 " Create a script that consists of the body of the function a:funcname.
 " Replace any ":return" by a ":finish", any argument variable by a global
-" variable, and and every ":call" by a ":source" for the next following argument
+" variable, and every ":call" by a ":source" for the next following argument
 " in the variable argument list.  This function is useful if similar tests are
 " to be made for a ":return" from a function call or a ":finish" in a script
 " file.