do not use `a' quoting style in comments

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/runit/runit_lib.h b/runit/runit_lib.h
index c36ea4c..c545616 100644
--- a/runit/runit_lib.h
+++ b/runit/runit_lib.h
@@ -13,7 +13,7 @@
    3. The name of the author may not be used to endorse or promote products
       derived from this software without specific prior written permission.
 
-THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR IMPLIED
 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,