Removed OpAtomicCompareExchangeWeak (#2665)

Verified locally by changing the version from `65536` to `66560` in `test/transcoding/atomics.spt`.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@62ea823e64307e8

Author: vmaksimo

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVInstruction.h

@@ -2799,6 +2799,12 @@ class SPIRVAtomicInstBase : public SPIRVInstTemplateBase {
     for (auto RC : getRequiredCapability())
       Module->addCapability(RC);
   }
+
+  void validate() const override {
+    if (OpCode == OpAtomicCompareExchangeWeak)
+      assert(this->getModule()->getSPIRVVersion() < VersionNumber::SPIRV_1_4 &&
+             "OpAtomicCompareExchangeWeak is removed starting from SPIR-V 1.4");
+  }
 };
 
 class SPIRVAtomicStoreInst : public SPIRVAtomicInstBase {