Fix broken links and typos (#5075)

* fix: links in communication section

* fix: typo

src/data/roadmaps/system-design/content/114-idempotent-operations.md

@@ -2,7 +2,7 @@
 
 Idempotent operations are operations that can be applied multiple times without changing the result beyond the initial application. In other words, if an operation is idempotent, it will have the same effect whether it is executed once or multiple times.
 
-It is also important to understand the benefits of [idempotent](https://en.wikipedia.org/wiki/Idempotence#Computer_science_meaning) operations, especially when using message or task queues that do not guarantee _exactly once_ processing. Many queueing systems guarantee _at least once_ message delivery or processing. These systems are not completely synchronized, for instance, across geographic regions, which simplifies some aspects of their implemntation or design. Designing the operations that a task queue executes to be idempotent allows one to use a queueing system that has accepted this design trade-off.
+It is also important to understand the benefits of [idempotent](https://en.wikipedia.org/wiki/Idempotence#Computer_science_meaning) operations, especially when using message or task queues that do not guarantee _exactly once_ processing. Many queueing systems guarantee _at least once_ message delivery or processing. These systems are not completely synchronized, for instance, across geographic regions, which simplifies some aspects of their implementation or design. Designing the operations that a task queue executes to be idempotent allows one to use a queueing system that has accepted this design trade-off.
 
 To learn more, visit the following links:
 

src/data/roadmaps/system-design/content/115-communication/101-tcp.md

@@ -18,7 +18,7 @@ Use TCP over UDP when:
 
 To learn more, visit the following links:
 
-- [What Is TCP?](https://github.com/donnemartin/system-design-primer#TCP)
+- [What Is TCP?](https://github.com/donnemartin/system-design-primer#transmission-control-protocol-tcp)
 - [What is the difference between HTTP protocol and TCP protocol?](https://www.quora.com/What-is-the-difference-between-HTTP-protocol-and-TCP-protocol)
 - [Networking for game programming](http://gafferongames.com/networking-for-game-programmers/udp-vs-tcp/)
 - [Key differences between TCP and UDP protocols](http://www.cyberciti.biz/faq/key-differences-between-tcp-and-udp-protocols/)

src/data/roadmaps/system-design/content/115-communication/103-rpc.md

@@ -34,4 +34,4 @@ RPC is focused on exposing behaviors. RPCs are often used for performance reason
 
 To learn more, visit the following links:
 
-- [What Is RPC?](https://github.com/donnemartin/system-design-primer#RPC)
+- [What Is RPC?](https://github.com/donnemartin/system-design-primer#remote-procedure-call-rpc)

src/data/roadmaps/system-design/content/115-communication/104-rest.md

@@ -13,5 +13,5 @@ REST is focused on exposing data. It minimizes the coupling between client/serve
 
 To learn more, visit the following links:
 
-- [What Is REST?](https://github.com/donnemartin/system-design-primer#REST)
+- [What Is REST?](https://github.com/donnemartin/system-design-primer#representational-state-transfer-rest)
 - [What are the drawbacks of using RESTful APIs?](https://www.quora.com/What-are-the-drawbacks-of-using-RESTful-APIs)