Consistent page title form and capitalization

[chalin]

This is what the side nav looks like for the semconv pages, as (soon to be) published on the OTel website:

(1) I'd like to suggest that all section titles (at this level and recurisively too) be of the form:

• Xxx Semantic Conventions

instead of "Semantic Conventions for Yyy".

(2) There should be consistency in capitalization. I'm ok with whichever convention you use:Title Case or Sentence case -- the latter being the Google dev docs recommendation).

(3) Some titles are "Semantic Convention", singular. This should be fixed.

WDYT @jsuereth @joaopgrassi

/cc @svrnm @cartermp

[chalin]

Here is what it would look like if the titles were fixed:

This is taken from the preview https://deploy-preview-2982--opentelemetry.netlify.app/docs/specs/semconv/ of

• Update semantic-conventions opentelemetry.io#2982

[chalin]

/assign