Fix a deprecation warning with newer Perl that breaks some tests.

--- a/tp/Texinfo/Parser.pm
+++ b/tp/Texinfo/Parser.pm
@@ -5438,12 +5438,12 @@
     }
   } elsif ($command eq 'clickstyle') {
     # REMACRO
-    if ($line =~ /^\s+@([[:alnum:]][[:alnum:]\-]*)({})?\s*/) {
+    if ($line =~ /^\s+@([[:alnum:]][[:alnum:]\-]*)(\{})?\s*/) {
       $args = ['@'.$1];
       $self->{'clickstyle'} = $1
         unless(_ignore_global_commands($self));
       $remaining = $line;
-      $remaining =~ s/^\s+@([[:alnum:]][[:alnum:]\-]*)({})?\s*(\@(c|comment)((\@|\s+).*)?)?//;
+      $remaining =~ s/^\s+@([[:alnum:]][[:alnum:]\-]*)(\{})?\s*(\@(c|comment)((\@|\s+).*)?)?//;
       $has_comment = 1 if (defined($4));
     } else {
       $self->line_error (sprintf($self->__(
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<tr><td><span title='2021-07-18 19:50:01 +0200'>2021-07-18</span></td><td><a href='/guix/commit/gnu/packages/gettext.scm?id=0e47fcced442d8e7c1b05184fdc1c14f10ed04ec'>Merge branch 'master' into core-updates</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-02 01:28:21 +0200'>2021-07-02</span></td><td><a href='/guix/commit/gnu/packages/gettext.scm?id=a597ddea423801158eaae7166e1730b10d0280e6'>gnu: po4a: Update to 0.63.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/gettext.scm (po4a): Update to 0.63.

Signed-off-by: Julien Lepiller &lt;julien@lepiller.eu&gt;
</span></span></td><td>EuAndreh via Guix-patches via</td></tr>