[lldb/Formatters] Remove space from vector type string summaries (NFCI)

This patch changes the string summaries for vector types by removing the
space between the type and the bracket, conforming to 277623f4.

This should also fix TestCompactVectors failure.

Differential Revision: https://reviews.llvm.org/D112340



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>