Remove duplicated code

(cherry picked from commit 4d093f8)

Author: shahmishal

test/lit.cfg

@@ -2135,13 +2135,6 @@ config.environment['SWIFT_DEBUG_ENABLE_COW_CHECKS'] = 'false'
 # Add this to the command which runs an executable to enable COW checks in the swift runtime.
 config.substitutions.append(('%enable-cow-checking', TARGET_ENV_PREFIX + 'SWIFT_DEBUG_ENABLE_COW_CHECKS=true;'))
 
-# Disabe COW sanity checks in the swift runtime by default.
-# (But it's required to set this environment variable to something)
-config.environment['SWIFT_DEBUG_ENABLE_COW_CHECKS'] = 'false'
-
-# Add this to the command which runs an executable to enable COW checks in the swift runtime.
-config.substitutions.append(('%enable-cow-checking', TARGET_ENV_PREFIX + 'SWIFT_DEBUG_ENABLE_COW_CHECKS=true;'))
-
 if config.lldb_build_root != "":
     lldb_python_path = get_lldb_python_path(config.lldb_build_root)
     lldb_python_interpreter = get_lldb_python_interpreter(config.lldb_build_root)