Docs: Update _index.md to use more appropriate grammar

[GLStephen]

This is just a simple grammar fix.

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[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[codecov]

Codecov Report

Merging #8484 (cc8089a) into main (290280e) will decrease coverage by 5.27%.
The diff coverage is 55.02%.

@@            Coverage Diff             @@
##             main    #8484      +/-   ##
==========================================
- Coverage   70.48%   65.21%   -5.27%     
==========================================
  Files         515      602      +87     
  Lines       23150    29886    +6736     
==========================================
+ Hits        16317    19491    +3174     
- Misses       5776     8923    +3147     
- Partials     1057     1472     +415     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/completion.go	13.04% <0.00%> (-1.25%)	⬇️
cmd/skaffold/app/cmd/config/list.go	65.21% <ø> (ø)
cmd/skaffold/app/cmd/config/set.go	88.72% <ø> (ø)
cmd/skaffold/app/cmd/config/util.go	54.28% <ø> (ø)
cmd/skaffold/app/cmd/credits.go	100.00% <ø> (ø)
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/generate_pipeline.go	60.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_modules.go	65.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_profiles.go	66.66% <ø> (ø)
... and 425 more

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[aaron-prindle]

Thanks for the fix here @GLStephen! The one failing test is around the commit message, for future information - skaffold uses the ConventionalCommit standard and has a test around commit messages having a format with a category prefix such as docs: in this case:

docs: Update _index.md to use more appropriate grammar

I can change the commit message when I merge so I can merge this, just a heads up on any future PRs. Thanks!