doc: fix backticks in fs API docs

PR-URL: #44962
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

Author: LiviaMedeiros

doc/api/fs.md

@@ -906,7 +906,7 @@ added: v10.0.0
 changes:
   - version: v14.0.0
     pr-url: https://github.com/nodejs/node/pull/27044
-    description: Changed 'flags' argument to 'mode' and imposed
+    description: Changed `flags` argument to `mode` and imposed
                  stricter type validation.
 -->
 
@@ -2203,7 +2203,7 @@ changes:
                  `ERR_INVALID_CALLBACK`.
   - version: v14.0.0
     pr-url: https://github.com/nodejs/node/pull/27044
-    description: Changed 'flags' argument to 'mode' and imposed
+    description: Changed `flags` argument to `mode` and imposed
                  stricter type validation.
 -->
 
@@ -5041,7 +5041,7 @@ added: v8.5.0
 changes:
   - version: v14.0.0
     pr-url: https://github.com/nodejs/node/pull/27044
-    description: Changed 'flags' argument to 'mode' and imposed
+    description: Changed `flags` argument to `mode` and imposed
                  stricter type validation.
 -->