GDB/doc: Remove extraneous spaces from completion examples

GDB/doc: Remove extraneous spaces from completion examples

Completion results are usually different when the operation is applied
to a word that is or is not followed by a space.  In some cases they are
equivalent, however a space would not be produced if completion was used
earlier on in the word processed.

However in the manual we have completion examples given using a space
that actually prevents the example from working.  E.g.:

(gdb) info bre <TAB>

(nothing) and:

(gdb) info bre <TAB><TAB>
Display all 200 possibilities? (y or n)

as it now goes on to propose the entire symbol table, while:

(gdb) info bre<TAB>
(gdb) info breakpoints

does the right thing, but is not what is shown in the manual.

In other cases an extraneous space is used that does not correspond to
the actual completion pattern shown, which gives an impression of
sloppiness.

Remove extraneous spaces then from completion examples as appropriate.