Remove confusing description from Body field in Logs Data Model (#3827)

Related to
#3814

## Changes

Remove confusing description from Body field in Logs Data Model.

The description makes the specification not clear as the language
authors may understand that the Bridge API must only accept Body as
`string`.

Additionally, I do not think that the following recommendation is
actually a good one:

> First-party Applications SHOULD use a string message

---------

Co-authored-by: jack-berg <34418638+jack-berg@users.noreply.github.com>
Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>
Co-authored-by: Cijo Thomas <cithomas@microsoft.com>

CHANGELOG.md

@@ -22,6 +22,8 @@ release.
 
 - Fix `Resource` field type in Logs Data Model.
   ([#3826](https://github.com/open-telemetry/opentelemetry-specification/pull/3826))
+- Remove confusing description from `Body` field in Logs Data Model to make it clear the Bridge API must support a structured body.
+  ([#3827](https://github.com/open-telemetry/opentelemetry-specification/pull/3827))
 - Deconstruct number scalar type to double and signed integer.
   ([#3854](https://github.com/open-telemetry/opentelemetry-specification/pull/3854))
 

specification/logs/data-model.md

@@ -402,16 +402,14 @@ corresponding short names).
 
 ### Field: `Body`
 
-Type: any.
-
-Description: A value containing the body of the log record (see the description
-of `any` type above). Can be for example a human-readable string message
-(including multi-line) describing the event in a free form or it can be a
-structured data composed of arrays and maps of other values. First-party
-Applications SHOULD use a string message. However, a structured body SHOULD be
-used to preserve the semantics of structured logs emitted by Third-party
-Applications. Can vary for each occurrence of the event coming from the same
-source. This field is optional.
+Type: [`any`](#type-any).
+
+Description: A value containing the body of the log record. Can be for example
+a human-readable string message (including multi-line) describing the event in
+a free form or it can be a structured data composed of arrays and maps of other
+values. Body MUST support [`any` type](#type-any) to preserve the semantics of
+structured logs emitted by the applications. Can vary for each occurrence of the
+event coming from the same source. This field is optional.
 
 ### Field: `Resource`