Making some minor style/grammar edits. (#4965)

Author: egilmorez

packages/firebase/index.d.ts

@@ -1026,7 +1026,7 @@ declare namespace firebase {
     /** Always set to PROJECT_ID */
     aud: string;
 
-    /** The user's unique id */
+    /** The user's unique ID */
     sub: string;
 
     /** The token issue time, in seconds since epoch */
@@ -1035,7 +1035,7 @@ declare namespace firebase {
     /** The token expiry time, normally 'iat' + 3600 */
     exp: number;
 
-    /** The user's unique id, must be equal to 'sub' */
+    /** The user's unique ID. Must be equal to 'sub' */
     user_id: string;
 
     /** The time the user authenticated, normally 'iat' */

packages/util/src/emulator.ts

@@ -40,7 +40,7 @@ interface FirebaseIdToken {
   // Always set to PROJECT_ID
   aud: string;
 
-  // The user's unique id
+  // The user's unique ID
   sub: string;
 
   // The token issue time, in seconds since epoch
@@ -49,7 +49,7 @@ interface FirebaseIdToken {
   // The token expiry time, normally 'iat' + 3600
   exp: number;
 
-  // The user's unique id, must be equal to 'sub'
+  // The user's unique ID. Must be equal to 'sub'
   user_id: string;
 
   // The time the user authenticated, normally 'iat'