fix: remove blank default values from press section schemas

Shopify rejects sections with empty string defaults on textarea/text
settings. Remove default="" from intro_text (hero) and source (quotes)
so the sections save without schema errors.

https://claude.ai/code/session_01YYptL6XzKziDt7xGKhz4Tn

Author: claude

sections/gk-press-hero.liquid

@@ -263,7 +263,6 @@
       "type": "textarea",
       "id": "intro_text",
       "label": "Intro Paragraph (optional)",
-      "default": "",
       "info": "Optional second line of supporting copy beneath the subheading."
     },
     {

sections/gk-press-quotes.liquid

@@ -281,7 +281,6 @@
           "type": "text",
           "id": "source",
           "label": "Source Label (optional)",
-          "default": "",
           "info": "Optional secondary line below attribution — e.g. an article title or date."
         },
         {
@@ -303,7 +302,6 @@
           "settings": {
             "quote": "The best guitarist working today.",
             "attribution": "Palm Beach Arts Paper",
-            "source": "",
             "emphasis": true
           }
         },
@@ -312,7 +310,6 @@
           "settings": {
             "quote": "A master of tone, groove, and musical personality.",
             "attribution": "Vintage Guitar Magazine",
-            "source": "",
             "emphasis": false
           }
         },
@@ -321,7 +318,6 @@
           "settings": {
             "quote": "Add Joe Bonamassa quote here — enter the approved wording in the theme editor.",
             "attribution": "Joe Bonamassa",
-            "source": "",
             "emphasis": false
           }
         }