Mass-replace blurb with seo:description in frontmatter

content/references/http-websocket-apis/public-api-methods/ledger-methods/ledger.md

@@ -1,7 +1,8 @@
 ---
 html: ledger.html # Watch carefully for clashes w/ this filename
 parent: ledger-methods.html
-blurb: Get info about a ledger version.
+seo:
+    description: Get info about a ledger version.
 labels:
   - Blockchain
 ---

content/references/http-websocket-apis/public-api-methods/ledger-methods/ledger_closed.md

@@ -1,7 +1,8 @@
 ---
 html: ledger_closed.html
 parent: ledger-methods.html
-blurb: Get the latest closed ledger version.
+seo:
+    description: Get the latest closed ledger version.
 labels:
   - Blockchain
 ---

content/references/http-websocket-apis/public-api-methods/ledger-methods/ledger_current.md

@@ -1,7 +1,8 @@
 ---
 html: ledger_current.html
 parent: ledger-methods.html
-blurb: Get the current working ledger version.
+seo:
+    description: Get the current working ledger version.
 labels:
   - Blockchain
 ---

content/references/http-websocket-apis/public-api-methods/ledger-methods/ledger_data.md

@@ -1,7 +1,8 @@
 ---
 html: ledger_data.html
 parent: ledger-methods.html
-blurb: Get the raw contents of a ledger version.
+seo:
+    description: Get the raw contents of a ledger version.
 labels:
   - Blockchain
   - Data Retention

content/references/http-websocket-apis/public-api-methods/ledger-methods/ledger_entry.md

@@ -1,7 +1,8 @@
 ---
 html: ledger_entry.html
 parent: ledger-methods.html
-blurb: Get one element from a ledger version.
+seo:
+    description: Get one element from a ledger version.
 labels:
   - Blockchain
   - Data Retention