remove is tighter on custom operator

This may be highly subjective, but to me postfixes are naturally
tighter than prefixes. In other words, I'd expect `-1!` to mean
`-(1!)`, not `(-1)!`. Compensated a test accordingly.

source/index.html

@@ -70,13 +70,13 @@ <h3 class="h2 trim-top">Jump in!</h3>
 say <span class="Special">&quot;</span><span class="Constant">Fibonacci number #8 is </span><span class="Identifier">@</span><span class="Identifier">fib</span>[<span class="Constant">7</span>]<span class="Special">&quot;</span><span class="Statement">;</span></pre></div>
       </div>
       <div role="tabpanel" class="tab-pane" id="samp-ops">
-<div class="highlight"><pre><span class="Statement">sub</span> postfix<span class="Statement">:</span><span class="Special">&lt;</span><span class="Constant">!</span><span class="Special">&gt;</span> (<span class="Type">Int</span> <span class="Identifier">$n</span>) <span class="PreProc">is</span> <span class="Special">tighter</span>(<span class="Identifier">&amp;</span><span class="Identifier">infix</span><span class="Statement">:</span><span class="Special">&lt;</span><span class="Constant">*</span><span class="Special">&gt;</span>) {
+<div class="highlight"><pre><span class="Statement">sub</span> postfix<span class="Statement">:</span><span class="Special">&lt;</span><span class="Constant">!</span><span class="Special">&gt;</span> (<span class="Type">Int</span> <span class="Identifier">$n</span>) {
     <span class="Statement">fail</span> <span class="Special">&quot;</span><span class="Constant">Not a Natural Number in Factorial</span><span class="Special">&quot;</span> <span class="Statement">if</span> <span class="Identifier">$n</span> <span class="Statement">&lt;</span> <span class="Constant">0</span><span class="Statement">;</span>
     <span class="Statement">[*]</span> <span class="Constant">2</span><span class="Statement">..</span><span class="Identifier">$n</span>
 }
 
 <span class="PreProc">use</span> Test<span class="Statement">;</span>
-isa-ok <span class="Constant">-1</span><span class="Special">!</span><span class="Statement">,</span> <span class="Type">Failure</span><span class="Statement">,</span> <span class="Special">&quot;</span><span class="Constant">Factorial for -1 fails</span><span class="Special">&quot;</span><span class="Statement">;</span>
+isa-ok (<span class="Constant">-1</span>)<span class="Special">!</span><span class="Statement">,</span> <span class="Type">Failure</span><span class="Statement">,</span> <span class="Special">&quot;</span><span class="Constant">Factorial for -1 fails</span><span class="Special">&quot;</span><span class="Statement">;</span>
 ok <span class="Constant">0</span><span class="Special">!</span> <span class="Statement">==</span> <span class="Constant">1</span><span class="Statement">,</span> <span class="Special">&quot;</span><span class="Constant">Factorial for 0</span><span class="Special">&quot;</span><span class="Statement">;</span>
 ok <span class="Constant">1</span><span class="Special">!</span> <span class="Statement">==</span> <span class="Constant">1</span><span class="Statement">,</span> <span class="Special">&quot;</span><span class="Constant">Factorial for 1</span><span class="Special">&quot;</span><span class="Statement">;</span>
 ok <span class="Constant">5</span><span class="Special">!</span> <span class="Statement">==</span> <span class="Constant">120</span><span class="Statement">,</span> <span class="Special">&quot;</span><span class="Constant">Factorial for a larger integer</span><span class="Special">&quot;</span><span class="Statement">;</span></pre></div>