Fix some fetcher tests

[Siedlerchr]

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[Siedlerchr]

@koppor The RFC fetcher fails due to your changes from #8238 for the comments field:

Notice the difference int the first two lines:

Expected:

Optional[%% You should probably cite draft-ietf-http-v10-spec instead of this I-D,@techreport{fielding-http-spec-01,
  abstract = {The Hypertext Transfer Protocol (HTTP) is an application-level protocol with the lightness and speed necessary for distributed, collaborative, hypermedia information systems. It is a generic, stateless, object-oriented protocol which can be used for many tasks, such as name servers and distributed object management systems, through extension of its request methods (commands). A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred. HTTP has been in use by the World-Wide Web global information initiative since 1990. This specification reflects preferred usage of the protocol referred to as 'HTTP/1.0', and is compatible with the most commonly used HTTP server and client programs implemented prior to November 1994.},
  author = {Henrik Nielsen and Roy T. Fielding and Tim Berners-Lee},
  day = {20},
  institution = {Internet Engineering Task Force},
  month = {#dec#},
  note = {Work in Progress},
  number = {draft-fielding-http-spec-01},
  pagetotal = {41},
  publisher = {Internet Engineering Task Force},
  title = {{Hypertext Transfer Protocol -- HTTP/1.0}},
  type = {Internet-Draft},
  url = {https://datatracker.ietf.org/doc/html/draft-fielding-http-spec-01},
  year = {1994},
  _jabref_shared = {sharedId: -1, version: 1}
}]

actual:

Optional[%% You should probably cite draft-ietf-http-v10-spec instead of this I-D.
@techreport{fielding-http-spec-01,
  abstract = {The Hypertext Transfer Protocol (HTTP) is an application-level protocol with the lightness and speed necessary for distributed, collaborative, hypermedia information systems. It is a generic, stateless, object-oriented protocol which can be used for many tasks, such as name servers and distributed object management systems, through extension of its request methods (commands). A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred. HTTP has been in use by the World-Wide Web global information initiative since 1990. This specification reflects preferred usage of the protocol referred to as 'HTTP/1.0', and is compatible with the most commonly used HTTP server and client programs implemented prior to November 1994.},
  author = {Henrik Nielsen and Roy T. Fielding and Tim Berners-Lee},
  day = {20},
  institution = {Internet Engineering Task Force},
  month = {#dec#},
  note = {Work in Progress},
  number = {draft-fielding-http-spec-01},
  pagetotal = {41},
  publisher = {Internet Engineering Task Force},
  title = {{Hypertext Transfer Protocol -- HTTP/1.0}},
  type = {Internet-Draft},
  url = {https://datatracker.ietf.org/doc/html/draft-fielding-http-spec-01},
  year = {1994},
  _jabref_shared = {sharedId: -1, version: 1}
}]

Probably related code:

jabref/src/main/java/org/jabref/model/entry/BibEntry.java

Lines 699 to 701 in 578c106

	public void setCommentsBeforeEntry(String parsedComments) {
	this.commentsBeforeEntry = parsedComments;
	}