Convert GlobalMCCache docstring to just a comment

Author: mhauru

src/copyable_task.jl

@@ -113,17 +113,12 @@ struct CacheKey
     key::Any
 end
 
-"""
-    GlobalMCCache
-
-A cache for holding MistyClosures, keyed by CacheKey.
-
-The reason to have a type for this, rather than just a global const
-Dict{CacheKey,MistyClosure}, is thread-safety. The global cache is written to when new
-TapedTasks are compiled, and if multiple threads are doing this concurrently races might
-occur. This type uses a ReentrantLock to ensure that any `setindex!` operations are atomic,
-solving the problem.
-"""
+# A cache for holding MistyClosures, keyed by CacheKey.
+# The reason to have a type for this, rather than just a global const
+# Dict{CacheKey,MistyClosure}, is thread-safety. The global cache is written to when new
+# TapedTasks are compiled, and if multiple threads are doing this concurrently races might
+# occur. This type uses a ReentrantLock to ensure that any `setindex!` operations are
+# atomic, solving the problem.
 struct GlobalMCCache
     cache::Dict{CacheKey,MistyClosure}
     lock::ReentrantLock