[Truffle] Untagged some passing Hash#fetch specs.

Author: nirvdrum

spec/truffle/tags/core/hash/fetch_tags.txt

@@ -1,6 +1,2 @@
 fails:Hash#fetch returns the value for key
-fails:Hash#fetch raises a KeyError if key is not found
 fails:Hash#fetch returns default if key is not found when passed a default
-fails:Hash#fetch returns value of block if key is not found when passed a block
-fails:Hash#fetch gives precedence to the default block over the default argument when passed both
-fails:Hash#fetch raises an ArgumentError when not passed one or two arguments