STYLE: Remove local ostringstream loc variable from ExceptionObject

The name `loc` was somewhat confusing here, as it is used elsewhere in
ExceptionObject as the parameter name for the `ITK_LOCATION` argument (the name
or signature of the function that threw the exception). Moreover, the use of a
string stream is no longer necessary, now that we can use `std::to_string`.

Author: N-Dekker

Modules/Core/Common/src/itkExceptionObject.cxx

@@ -41,11 +41,8 @@ class ExceptionObject::ExceptionData
     , m_File(std::move(file))
     , m_Line(line)
   {
-    std::ostringstream loc;
-
-    loc << ':' << m_Line << ":\n";
     m_What = m_File;
-    m_What += loc.str();
+    m_What += ':' + std::to_string(m_Line) + ":\n";
     m_What += m_Description;
   }