fix comment typo

Author: AArnott

LibGit2Sharp/Core/Handles/Libgit2Object.cs

@@ -1,7 +1,7 @@
 // This activates a lightweight mode which will help put under the light
 // incorrectly released handles by outputing a warning message in the console.
 //
-// This should be activated when tests are being run of the CI server.
+// This should be activated when tests are being run on the CI server.
 //
 // Uncomment the line below or add a conditional symbol to activate this mode