rpc: remove info about mallocinfo needing glibc 2.10+ #23643

We require glibc 2.18+.

@fanquake It would greatly help if you explained why you made the changes the way you created them. For example, you might have changed from:

"mallocinfo is only available when compiled with glibc 2.10+"

to

"mallocinfo is only available when compiled with glibc 2.18+"

So why did you prefer not to mention glibc at all?

ACK 9a09d307e9bd81ed218dd560d3eac7565f1f7a2f @shaavan I think you have a misconception with your comment. mallocinfo does not need glibc2.18. We require glibc2.18+ to build Bitcoin Core (since #23511).

The current comment is more information than is needed. If a user has built Bitcoin Core with < glibc2.10, then they most likely made that choice explicitly. They don't need to be reminded about what situations it would be available, nor is it our job.

For example, you might have changed from: to

That wouldn't be correct. malloc_info was added to glibc in version 2.10.

So why did you prefer not to mention glibc at all?

Warning that a certain feature is only available if you're using glibc 2.10+, is redundant if our binaries already require 2.18+.

Thank you, @jarolrod and @fanquake, for correcting my assessment of this PR. I understand now that mentioning about gilbc version in this error message is redundant information and needs to be edited out.

ACK 9a09d307e9bd81ed218dd560d3eac7565f1f7a2f