feat: Change order of database courses

Author: hq-jiang

README.md

@@ -314,8 +314,8 @@ Courses | Duration | Effort | Prerequisites | Discussion
 
 Courses | Duration | Effort | Prerequisites | Discussion
 :-- | :--: | :--: | :--: | :--:
-[Relational Databases and SQL](https://www.edx.org/course/databases-5-sql)| 2 weeks | 10 hours/week | core programming | [chat](https://discord.gg/P8SPPyF)
 [Databases: Modeling and Theory](https://www.edx.org/course/modeling-and-theory)| 2 weeks | 10 hours/week | core programming | [chat](https://discord.gg/pMFqNf4)
+[Databases: Relational Databases and SQL](https://www.edx.org/course/databases-5-sql)| 2 weeks | 10 hours/week | core programming | [chat](https://discord.gg/P8SPPyF)
 [Databases: Semistructured Data](https://www.edx.org/course/semistructured-data)| 2 weeks | 10 hours/week | core programming | [chat](https://discord.gg/duCJ3GN)
 [Machine Learning](https://www.coursera.org/learn/machine-learning)| 11 weeks | 4-6 hours/week | linear algebra | [chat](https://discord.gg/NcXHDjy)
 [Computer Graphics](https://www.edx.org/course/computer-graphics-uc-san-diegox-cse167x)| 6 weeks | 12 hours/week | C++ or Java, linear algebra | [chat](https://discord.gg/68WqMNV)