Don't check for presence of ENV['GITHUB_WORKFLOW']

We already check whether `ENV['GITHUB_WORKFLOW']` is equal to `Compilations`,
so we don't need to check that it's not nil.

Author: peterzhu2118

bootstraptest/test_ractor.rb

@@ -214,10 +214,8 @@
 ###
 ###
 # Ractor still has several memory corruption so skip huge number of tests
-if ENV['GITHUB_WORKFLOW'] &&
-   (ENV['GITHUB_WORKFLOW'] == 'Compilations' ||
-   ENV['GITHUB_WORKFLOW'] == 'ModGC')
-   # ignore the follow
+if ENV['GITHUB_WORKFLOW'] == 'Compilations' || ENV['GITHUB_WORKFLOW'] == 'ModGC'
+  # ignore the follow
 else
 
 # Ractor.select(*ractors) receives a values from a ractors.