[tab:container.seq.opt] Remove blank line in the description of emplace_back.

Author: Dawn Perchik

source/containers.tex

@@ -1111,7 +1111,7 @@
  \effects Appends an object of type \tcode{T} constructed with \tcode{std::forward<\brk{}Args\brk{}>(\brk{}args)...}.\br
  \expects \tcode{T} is \oldconcept{EmplaceConstructible} into \tcode{X} from \tcode{args}. For \tcode{vector}, \tcode{T}
  is also
- \oldconcept{MoveInsertable} into \tcode{X}.\br
+ \oldconcept{MoveInsertable} into \tcode{X}.
  \returns \tcode{a.back()}.  &
  \tcode{deque},
  \tcode{list},