doc: fix use of "e.g." in stdbuf help message

"E.g." stands for latin "exempli gratia" which is typically read
as "for example".  "E.g." does not stand for the word "example".
As such, "for e.g." might be read as "for for example".

Fix this usage by simply replacing "e.g." with "example".

src/stdbuf.c

@@ -115,7 +115,7 @@ size set to MODE bytes.\n\
 "), stdout);
       fputs (_("\n\
 NOTE: If COMMAND adjusts the buffering of its standard streams ('tee' does\n\
-for e.g.) then that will override corresponding settings changed by 'stdbuf'.\n\
+for example) then that will override corresponding changes by 'stdbuf'.\n\
 Also some filters (like 'dd' and 'cat' etc.) don't use streams for I/O,\n\
 and are thus unaffected by 'stdbuf' settings.\n\
 "), stdout);