Mass-replace blurb with seo:description in frontmatter

content/references/http-websocket-apis/public-api-methods/server-info-methods/fee.md

@@ -1,7 +1,8 @@
 ---
 html: fee.html
 parent: server-info-methods.html
-blurb: Get information about transaction cost.
+seo:
+    description: Get information about transaction cost.
 labels:
   - Fees
 ---

content/references/http-websocket-apis/public-api-methods/server-info-methods/manifest.md

@@ -1,7 +1,8 @@
 ---
 html: manifest.html
 parent: server-info-methods.html
-blurb: Look up the public information about a known validator.
+seo:
+    description: Look up the public information about a known validator.
 labels:
   - Blockchain
 ---

content/references/http-websocket-apis/public-api-methods/server-info-methods/server_definitions.md

@@ -1,7 +1,8 @@
 ---
 html: server_definitions.html
 parent: server-info-methods.html
-blurb: Retrieve an SDK-compatible `definitions.json`, generated from the `rippled` instance currently running.
+seo:
+    description: Retrieve an SDK-compatible `definitions.json`, generated from the `rippled` instance currently running.
 labels:
   - Core Server
 ---

content/references/http-websocket-apis/public-api-methods/server-info-methods/server_info.md

@@ -1,7 +1,8 @@
 ---
 html: server_info.html
 parent: server-info-methods.html
-blurb: Retrieve status of the server in human-readable format.
+seo:
+    description: Retrieve status of the server in human-readable format.
 labels:
   - Core Server
 ---

content/references/http-websocket-apis/public-api-methods/server-info-methods/server_state.md

@@ -1,7 +1,8 @@
 ---
 html: server_state.html
 parent: server-info-methods.html
-blurb: Retrieve status of the server in machine-readable format.
+seo:
+    description: Retrieve status of the server in machine-readable format.
 labels:
   - Core Server
 ---