Fix minor doc issues in ADR 187 and ADR 189

Use "in the future" instead of "in future" in ADR 187 for consistent
phrasing. Escape pipe characters in ADR 189 table cells to prevent
Markdown parser column-count misinterpretation.

Author: wmadden

docs/architecture docs/adrs/ADR 187 - MongoDB schema representation for migration diffing.md

@@ -94,7 +94,7 @@ interface MongoSchemaIR {
 
 An empty IR (for a new project with no prior contract) is `{ collections: {} }`.
 
-A collection groups its indexes (and, in future, its validator and options):
+A collection groups its indexes (and, in the future, its validator and options):
 
 ```ts
 class MongoSchemaCollection extends MongoSchemaNode {

docs/architecture docs/adrs/ADR 189 - Structural index matching for MongoDB migrations.md

@@ -48,10 +48,10 @@ Two indexes that produce the same lookup key are the same index. For example:
 
 | Index                           | Lookup key               |
 | ------------------------------- | ------------------------ |
-| `{ email: 1 }`, unique          | `email:1|unique`         |
+| `{ email: 1 }`, unique          | `email:1\|unique`        |
 | `{ email: 1 }`, not unique      | `email:1`                |
 | `{ lastName: 1, firstName: 1 }` | `lastName:1,firstName:1` |
-| `{ createdAt: 1 }`, TTL 86400s  | `createdAt:1|ttl:86400`  |
+| `{ createdAt: 1 }`, TTL 86400s  | `createdAt:1\|ttl:86400` |
 
 
 The planner builds a `Map<string, MongoSchemaIndex>` for both origin and destination, then diffs the key sets: