Hardcode github code location temporarily.

See spring-cloud/spring-cloud-build#244

Fixes gh-3155

docs/modules/ROOT/pages/spring-cloud-gateway/gatewayfilter-factories/tokenrelay-factory.adoc

@@ -87,7 +87,7 @@ To enable this for Spring Cloud Gateway add the following dependencies
 
 - `org.springframework.boot:spring-boot-starter-oauth2-client`
 
-How does it work?  The {github-code}/src/main/java/org/springframework/cloud/gateway/security/TokenRelayGatewayFilterFactory.java[filter]
+How does it work?  The https://github.com/spring-cloud/spring-cloud-gateway/blob/main/spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/factory/TokenRelayGatewayFilterFactory.java[filter]
 extracts an OAuth2 access token from the currently authenticated user for the provided `clientRegistrationId`.
 If no `clientRegistrationId` is provided, the currently authenticated user's own access token (obtained during login) is used.
 In either case, the extracted access token is placed in a request header for the downstream requests.

docs/modules/ROOT/pages/spring-cloud-gateway/glossary.adoc

@@ -6,6 +6,6 @@
 It is defined by an ID, a destination URI, a collection of predicates, and a collection of filters. A route is matched if the aggregate predicate is true.
 * *Predicate*: This is a https://docs.oracle.com/javase/8/docs/api/java/util/function/Predicate.html[Java 8 Function Predicate]. The input type is a https://docs.spring.io/spring/docs/5.0.x/javadoc-api/org/springframework/web/server/ServerWebExchange.html[Spring Framework `ServerWebExchange`].
 This lets you match on anything from the HTTP request, such as headers or parameters.
-* *Filter*: These are instances of {github-code}/spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/GatewayFilter.java[`GatewayFilter`] that have been constructed with a specific factory.
+* *Filter*: These are instances of https://github.com/spring-cloud/spring-cloud-gateway/blob/main/spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/GatewayFilter.java[`GatewayFilter`] that have been constructed with a specific factory.
 Here, you can modify requests and responses before or after sending the downstream request.