Porting/updateAUTHORS.pl: Suggested `git config` command is wrong

When you run tests in a repository that has local modifications
`t/porting/authors.t` checks if your git is correctly configured
with your identity.  However, the suggested commands don't work,
because `git config` doesn't need a `--set` flag to set options.

This patch removes the `--set` from the suggested commands which is
not necessary to set the variables in the local git repository. For
comparison, if you run `git commit` without your identity set up, it
suggests:

```
Run

  git config --global user.email "you@example.com"
  git config --global user.name "Your Name"

to set your account's default identity.
Omit --global to set the identity only in this repository.
```

1 files changed, 4 insertions, 4 deletions

diff --git a/Porting/updateAUTHORS.pl b/Porting/updateAUTHORS.pl
index b3094e41d3..e0d52ea0af 100755
--- a/Porting/updateAUTHORS.pl
+++ b/Porting/updateAUTHORS.pl
@@ -285,8 +285,8 @@ sub error_advice_for_uncommitted_changes {
     else {
         $extra .=
               "\nYou do not have any git user config set up, consider using\n\n"
-            . "    git config --set user.name 'Your Name'\n"
-            . "    git config --set user.email 'your\@email.com'\n\n";
+            . "    git config user.name 'Your Name'\n"
+            . "    git config user.email 'your\@email.com'\n\n";
     }
 
     my $props= "";
@@ -367,8 +367,8 @@ To resolve this you can perform one or more of these steps:
        havent configured your git details properly, in which case you
        can use something like the following commands:
 
-            git config --set user.name "Some Name"
-            git config --set user.email "somewhere\@provider"
+            git config user.name "Some Name"
+            git config user.email "somewhere\@provider"
 
        If you are known to the project already this is all you need to
        do. If you are not then you should perform option 2 or 4 as well