Fix gendered documentation

[pedro.gonnet]

Summary

Changed two references to developers as "he" or "him" to the more neutral "they".

[sylvestre.ledru]

thanks!

[JDevlieghere]

Thank you!

[keryell]

clang-tools-extra/docs/clang-tidy/checks/google-objc-global-variable-declaration.rst

47

I wonder whether it would not be more coherent to have more than 1 user here.
But this is just a French point-of-view. :-)

clang-tools-extra/docs/clang-tidy/checks/google-objc-global-variable-declaration.rst

 
 However for code that prefixed with non-alphabetical characters like:
 
 .. code-block:: objc
 
   static NSString* __anotherString = @"world";
 
 The check will give a warning message but will not be able to suggest a fix. The
-user need to fix it on his own.
+user needs to fix it on their own.

lldb/docs/use/variable.rst

 Filters
 -------
 
 Filters are a solution to the display of complex classes. At times, classes
 have many member variables but not all of these are actually necessary for the
 user to see.
 
 A filter will solve this issue by only letting the user see those member
-variables he cares about. Of course, the equivalent of a filter can be
+variables they care about. Of course, the equivalent of a filter can be
 implemented easily using synthetic children, but a filter lets you get the job
 done without having to write Python code.
 
 For instance, if your class Foobar has member variables named A thru Z, but you
 only need to see the ones named B, H and Q, you can define a filter:
 
 ::