CI: Start all tests with bangline

Perl::Critic will think they're modules otherwise.

t/freed-bytes-commas.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/freed-bytes.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/link-counting.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/normal-linkage.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/normal-non-linkage.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/sha1collision-non-linkage.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/timestamp-preservation.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;
 

t/zero-size-non-linkage.t

@@ -1,3 +1,4 @@
+#!perl
 use strict;
 use warnings;