Change #!/usr/local/bin/perl to #!/usr/bin/perl in t/*.t

This doesn't really matter, since these are not executed directly, but
it's more consistent with everything else and modern systems.

t/chkstow.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/cleanup_invalid_links.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/cli.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/cli_options.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/defer.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/dotfiles.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/examples.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/find_stowed_path.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/foldable.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/ignore.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/join_paths.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/parent.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/rc_options.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/stow.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/unstow.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #

t/unstow_orig.t

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!/usr/bin/perl
 #
 # This file is part of GNU Stow.
 #