[pitivi] Fix minor typo: smoothenss -> smoothness

[Alexandru Băluț <alexbalut src gnome org>]

commit 83646d4b8c2a0e37bc3c1028c56846e8d07b39bc
Author: Yuri Chornoivan <yurchor ukr net>
Date:   Sun Jun 7 17:36:18 2020 +0000

    Fix minor typo: smoothenss -> smoothness

 help/C/transitions.page | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/help/C/transitions.page b/help/C/transitions.page
index 3730ccf8..ccf8aed5 100644
--- a/help/C/transitions.page
+++ b/help/C/transitions.page
@@ -47,7 +47,7 @@
     <p>The transitions can be further adjusted with the following options from the bottom of the 
<gui>Transition</gui> tab:</p>
     <list>
       <item>
-        <p><em>Normal mode</em> will apply the transition in a linear fashion over the whole overlapping 
region. When in normal mode, you can adjust the degree of sharpness/smoothenss of the transition.</p>
+        <p><em>Normal mode</em> will apply the transition in a linear fashion over the whole overlapping 
region. When in normal mode, you can adjust the degree of sharpness/smoothness of the transition.</p>
       </item>
       <item>
         <p><em>Loop</em> mode will apply the transition in a circular manner. When in loop mode, you can 
adjust the speed with which the transition will repeat itself.</p>