[XRay] Fix typo in docs. NFC

[dberris]

LGTM -- good catch, thanks!

[MaskRay]

rebase

llvm/trunk/docs/XRay.rst

::
   clang -fxray-instrument -fxray-instruction-threshold=1 ..
 
 You can also specifically instrument functions in your binary to either always
 or never be instrumented using source-level attributes. You can do it using the
 GCC-style attributes or C++11-style attributes.
 
 .. code-block:: c++
 
-    [[clang::xray_always_intrument]] void always_instrumented();
+    [[clang::xray_always_instrument]] void always_instrumented();
 
     [[clang::xray_never_instrument]] void never_instrumented();
 
-    void alt_always_instrumented() __attribute__((xray_always_intrument));
+    void alt_always_instrumented() __attribute__((xray_always_instrument));
 
     void alt_never_instrumented() __attribute__((xray_never_instrument));
 
 When linking a binary, you can either manually link in the `XRay Runtime
 Library`_ or use ``clang`` to link it in automatically with the
 ``-fxray-instrument`` flag. Alternatively, you can statically link-in the XRay
 runtime library from compiler-rt -- those archive files will take the name of
 `libclang_rt.xray-{arch}` where `{arch}` is the mnemonic supported by clang

llvm/trunk/docs/XRayExample.rst

 application.
 
 .. code-block:: c++
 
   // sample.cc
   #include <iostream>
   #include <thread>
 
-  [[clang::xray_always_intrument]] void f() {
+  [[clang::xray_always_instrument]] void f() {
     std::cerr << '.';
   }
 
-  [[clang::xray_always_intrument]] void g() {
+  [[clang::xray_always_instrument]] void g() {
     for (int i = 0; i < 1 << 10; ++i) {
       std::cerr << '-';
     }
   }
 
   int main(int argc, char* argv[]) {
     std::thread t1([] {
       for (int i = 0; i < 1 << 10; ++i)