Bump nokogiri from 1.10.7 to 1.13.6 in /sql/associations_exercise

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.7 to 1.13.6.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.10.7...v1.13.6)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

sql/associations_exercise/Gemfile.lock

@@ -99,11 +99,12 @@ GEM
     method_source (0.9.2)
     mimemagic (0.3.4)
     mini_mime (1.0.2)
-    mini_portile2 (2.4.0)
+    mini_portile2 (2.8.0)
     minitest (5.14.0)
     nio4r (2.5.2)
-    nokogiri (1.10.7)
-      mini_portile2 (~> 2.4.0)
+    nokogiri (1.13.6)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     pg (1.2.2)
     pry (0.12.2)
       coderay (~> 1.1.0)
@@ -112,6 +113,7 @@ GEM
       pry (>= 0.10.4)
     public_suffix (4.0.3)
     puma (3.12.2)
+    racc (1.6.0)
     rack (2.1.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)