glsl: Fix a comment typo in copy propagation.
diff --git a/src/glsl/opt_copy_propagation.cpp b/src/glsl/opt_copy_propagation.cpp
index 4ab23bf..387db64 100644
--- a/src/glsl/opt_copy_propagation.cpp
+++ b/src/glsl/opt_copy_propagation.cpp
@@ -191,7 +191,7 @@
       sig_param_iter.next();
    }
 
-   /* Since we're unlinked, we don't (necssarily) know the side effects of
+   /* Since we're unlinked, we don't (necessarily) know the side effects of
     * this call.  So kill all copies.
     */
    acp->make_empty();