Change gendered terms to be gender-neutral (#21325)

Some typos are also fixed.

src/libsystemd/sd-bus/bus-socket.c

@@ -301,8 +301,8 @@ static int verify_external_token(sd_bus *b, const char *p, size_t l) {
         uid_t u;
         int r;
 
-        /* We don't do any real authentication here. Instead, we if
-         * the owner of this bus wanted authentication he should have
+        /* We don't do any real authentication here. Instead, if 
+         * the owner of this bus wanted authentication they should have
          * checked SO_PEERCRED before even creating the bus object. */
 
         if (!b->anonymous_auth && !b->ucred_valid)

src/libsystemd/sd-bus/sd-bus.c

@@ -3283,7 +3283,7 @@ static int bus_poll(sd_bus *bus, bool need_more, uint64_t timeout_usec) {
                         return e;
 
                 if (need_more)
-                        /* The caller really needs some more data, he doesn't
+                        /* The caller really needs some more data, they don't
                          * care about what's already read, or any timeouts
                          * except its own. */
                         e |= POLLIN;