[FPEnv][BitcodeReader] Correct strictfp test.

Correct a strictfp test to follow the rules documented in the LangRef:
https://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics

This test needed the strictfp attribute added to a function definition.

Test changes verified with D146845.

Author: kpneal

llvm/unittests/Bitcode/BitReaderTest.cpp

@@ -160,7 +160,7 @@ TEST(BitReaderTest, MaterializeConstrainedFPStrictFP) {
   LLVMContext Context;
   std::unique_ptr<Module> M = getLazyModuleFromAssembly(
       Context, Mem,
-      "define double @foo(double %a) {\n"
+      "define double @foo(double %a) strictfp {\n"
       "  %result = call double @llvm.experimental.constrained.sqrt.f64(double "
       "%a, metadata !\"round.tonearest\", metadata !\"fpexcept.strict\") "
       "strictfp\n"