Typos in instructions for lab 15

[richardrigutins]

Module: 07

Lab/Demo: 15

Task: 00

Step: 00

Description of issue

There are some small typos in the instructions for lab 15 (instructions/15-cognitive-search.md). For example:

• Line 154: ... can pick right back up form the same ... should be ... can pick right back up from the same ....
• Line 213: ... giving a higher score to results that contains both terms ... should be ... giving a higher score to results that contain both terms ....

Repro steps:

1. Open the instructions for lab 15 (instructions/15-cognitive-search.md).

[MScalopez]

@richardrigutins thank you for bringing this to our attention, fixed the typos.