refactor(calc-01): remove redundant keyboard group titles

samples/calc-01/index.css

@@ -277,14 +277,6 @@ select {
   box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.05);
 }
 
-.group-title {
-  margin: 0 0 10px;
-  color: #dce4f0;
-  font-size: 12px;
-  text-transform: uppercase;
-  letter-spacing: 0.14em;
-}
-
 .key-grid {
   display: grid;
   gap: 10px;

samples/calc-01/index.html

@@ -47,17 +47,14 @@
 
       <div class="keyboard-layout">
         <section class="key-group key-group-functions" aria-label="Functions">
-          <div class="group-title">Functions</div>
           <div class="key-grid functions-grid" id="functionsButtons"></div>
         </section>
 
         <section class="key-group key-group-numbers" aria-label="Numbers">
-          <div class="group-title">Numbers</div>
           <div class="key-grid numbers-grid" id="numbersButtons"></div>
         </section>
 
         <section class="key-group key-group-operators" aria-label="Operators">
-          <div class="group-title">Operators</div>
           <div class="key-grid operators-grid" id="operatorsButtons"></div>
         </section>
       </div>