Update move-constructors-and-move-assignment-operators-cpp.md

Annotate the sample `MemoryBlock` move constructor and move assignment operator with `noexcept` so they correctly produce the expected behavior in the example which reallocates a vector of `MemoryBlock`.

Fixes VSO-1120480.

Drive-by: Cleanup handwavy sentence about "preserving the rvalue property".

Author: CaseyCarter

docs/cpp/move-constructors-and-move-assignment-operators-cpp.md

@@ -167,7 +167,7 @@ The following example shows the complete move constructor and move assignment op
 
 ```cpp
 // Move constructor.
-MemoryBlock(MemoryBlock&& other)
+MemoryBlock(MemoryBlock&& other) noexcept
    : _data(nullptr)
    , _length(0)
 {
@@ -186,7 +186,7 @@ MemoryBlock(MemoryBlock&& other)
 }
 
 // Move assignment operator.
-MemoryBlock& operator=(MemoryBlock&& other)
+MemoryBlock& operator=(MemoryBlock&& other) noexcept
 {
    std::cout << "In operator=(MemoryBlock&&). length = "
              << other._length << "." << std::endl;
@@ -292,15 +292,15 @@ If you provide both a move constructor and a move assignment operator for your c
 
 ```cpp
 // Move constructor.
-MemoryBlock(MemoryBlock&& other)
+MemoryBlock(MemoryBlock&& other) noexcept
    : _data(nullptr)
    , _length(0)
 {
    *this = std::move(other);
 }
 ```
 
-The [std::move](../standard-library/utility-functions.md#move) function preserves the rvalue property of the *other* parameter.
+The [std::move](../standard-library/utility-functions.md#move) function converts the lvalue `other` to an rvalue.
 
 ## See also