test: disable access merging optimization test with invariant asserts

Invariant checks add extra access markers and they made the optimized
code different than the expected one and made the test failed.
CI presets usually set `--no-swift-stdlib-assertion`, so no effect on
CI except for `buildbot_incremental_linux_crosscompile_wasm`.

Author: kateinoigakukun

test/SILOptimizer/merge_exclusivity.swift

@@ -1,5 +1,6 @@
 // RUN: %target-swift-frontend -O -enforce-exclusivity=checked -Xllvm -sil-disable-pass=redundant-load-elimination -emit-sil  -primary-file %s | %FileCheck %s --check-prefix=TESTSIL
 // REQUIRES: optimized_stdlib,asserts
+// REQUIRES: swift_stdlib_no_asserts
 // REQUIRES: PTRSIZE=64
 
 public var check: UInt64 = 0