feat(curriculum): replace placeholder text with intros for rdbms section (#43589)

* feat: add introsos for rdbms

* Update client/i18n/locales/english/intro.json

Co-authored-by: Sem Bauke <46919888+Sembauke@users.noreply.github.com>

* Update client/i18n/locales/english/intro.json

Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

* Update client/i18n/locales/english/intro.json

Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

Co-authored-by: Sem Bauke <46919888+Sembauke@users.noreply.github.com>
Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

client/i18n/locales/english/intro.json

@@ -296,11 +296,17 @@
   },
   "relational-databases": {
     "title": "Relational Databases",
-    "intro": ["placeholder"],
+    "intro": [
+      "For these courses, you will use real developer tools and software including VS Code, PostgreSQL, and the Linux / Unix command line to complete interactive tutorials and build projects."
+    ],
     "blocks": {
       "learn-relational-databases": {
         "title": "Learn Relational Databases",
-        "intro": ["placeholder"]
+        "intro": [
+          "These courses start off with basic Bash commands. Using the terminal, you will learn everything from navigating and manipulating a file system, scripting in Bash, all the way to advanced usage.",
+          "Next, you will learn how to create and work with relational databases using PostgreSQL, a database management system, and SQL, the language of these databases.",
+          "Finally, you will learn Git, the version control system, and GitHub, a code repository hosting service - two essential tools of every developer."
+        ]
       }
     }
   },