Update the tooltip 'Execute Query(F5)' to 'Execute query(F5)'

[v-xianya]

Storage Explorer Version: 1.8.0_20190425.8
Platform/OS: Linux Ubuntu/macOS High Sierra/Windows 10
Architecture: ia32/x64
Commit: f43a9ee4
Regression From: Not a regression

Steps to reproduce:

1. Expand a storage account -> Tables -> Create a new table.
2. Click 'Query' on the toolbar -> Hover the mouse on the Execute query button.
3. Check the tooltip.

Expect Experience:
Show 'Execute query(F5)'.

Actual Experience:
Show 'Execute Query(F5)'.

[MRayermannMSFT]

Fix checked into master. Please verify that all tooltips on those buttons still works. The query builder has not yet been made localizable, so I started working on that by doing the button tooltips.