servo: Merge #11877 - Fix README link (from shadow-fox:master); r=Manishearth

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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because Link change on the docs/HACKING_QUICKSTART.md Page.

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Source-Repo: https://github.com/servo/servo
Source-Revision: df21595765947e54b663a4370644c16f5c91334d

servo/docs/HACKING_QUICKSTART.md

@@ -9,7 +9,7 @@ on the [Github Workflow](https://github.com/servo/servo/wiki/Github-workflow) an
 
 ## Building Servo
 
-Building Servo is quite easy. Install the prerequisites described in the [README](./README.md) file. Then type:
+Building Servo is quite easy. Install the prerequisites described in the [README](../README.md) file. Then type:
 
 ```shell
 ./mach build -d