Fix documentation typos; NFC

Fixes bugprone-virtual-near-miss & performance-type-promotion-in-math-fn.

Author: bakinovsky-m

clang-tools-extra/docs/clang-tidy/checks/bugprone-virtual-near-miss.rst

@@ -15,6 +15,6 @@ Example:
   };
 
   struct Derived : Base {
-    virtual funk();
+    virtual void funk();
     // warning: 'Derived::funk' has a similar name and the same signature as virtual method 'Base::func'; did you mean to override it?
   };

clang-tools-extra/docs/clang-tidy/checks/performance-type-promotion-in-math-fn.rst

@@ -6,7 +6,7 @@ performance-type-promotion-in-math-fn
 Finds calls to C math library functions (from ``math.h`` or, in C++, ``cmath``)
 with implicit ``float`` to ``double`` promotions.
 
-For example, warns on ``::sin(0.f)``, because this funciton's parameter is a
+For example, warns on ``::sin(0.f)``, because this function's parameter is a
 double. You probably meant to call ``std::sin(0.f)`` (in C++), or ``sinf(0.f)``
 (in C).