DOCS-2456: edit hidden member text
Fix typo in Write Operation Performance

Signed-off-by: Sam Kleinman <samk@10gen.com>
Fix grammar mistake in Data Modeling Introduction

Missing "the"

Signed-off-by: Sam Kleinman <samk@10gen.com>
Fix grammar in Operational Factors and Data Models

Signed-off-by: Sam Kleinman <samk@10gen.com>
Fix mistake in Multikey Indexes

Signed-off-by: Sam Kleinman <samk@10gen.com>