tests: bluetooth: shell: Set min_flash to 145K

With recent master, this sample started to overflow ROM area of
arduino_101, which has 144K of it:

Memory region         Used Size  Region Size  %age Used
             ROM:      149420 B       144 KB    101.33%
             RAM:       26228 B        52 KB     49.26%
        IDT_LIST:         564 B         2 KB     27.54%
        MMU_LIST:          0 GB         1 KB      0.00%

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>