revert(commitlint): disable `signed-off-by` rule

The `signed-off-by` rule does not correctly detect the `Signed-off-by:`
trailer if it's not the last trailer. Therefore, this rule has been
disabled until we can resolve this in the commitlint upstream.

Change-Id: I50ea29067528f3c1c25beeea5eb25134b25b2af2
Signed-off-by: Chris Kay <chris.kay@arm.com>

commitlint.config.js

@@ -9,6 +9,6 @@ module.exports = {
     rules: {
         "header-max-length": [1, "always", config.maxHeaderWidth], /* Warning */
         "body-max-line-length": [1, "always", config.maxLineWidth], /* Warning */
-        "signed-off-by": [2, "always", "Signed-off-by:"] /* Error */
+        "signed-off-by": [0, "always", "Signed-off-by:"] /* Disabled - buggy */
     }
 };