Merge bitcoin/bitcoin#28304: doc: Remove confusing assert linter

fa6e6a3f03 doc: Remove confusing assert linter (MarcoFalke)

Pull request description:

  The `assert()` documentation and linter are redundant and confusing:

  * The source code already refuses to compile with `assert()` disabled.
  * They violate the assumptions about `Assert()`, which *requires* side effects.
  * The existing linter doesn't enforce the guideline, only checking for `++` and `--` side effects.

  Fix all issues by removing the docs and the linter. See also https://github.com/bitcoin/bitcoin/pull/26684#discussion_r1287370102

  Going forward everyone is free to use whatever code in this regard they think is the easiest to read. Also, everyone is still free to share style-nits, if they think it is a good use of their time and of the pull request author. Finally, the author is still free to dismiss or ignore this style-nit, or any other style-nit.

ACKs for top commit:
  hebasto:
    ACK fa6e6a3f03, I have reviewed the code and it looks OK.
  theStack:
    ACK fa6e6a3f03

Tree-SHA512: 686738d71e1316cc95e5d3f71869b55a02bfb137c795cc0875057f4410e564bc8eff03c985a2087b007fb08fc84551c7da1e8b30c7a9c3f2b14e5e44a5970236

test/lint/lint-assertions.py

@@ -23,20 +23,10 @@ def git_grep(params: [], error_msg: ""):
 
 
 def main():
-    # PRE31-C (SEI CERT C Coding Standard):
-    # "Assertions should not contain assignments, increment, or decrement operators."
-    exit_code = git_grep([
-        "-E",
-        r"[^_]assert\(.*(\+\+|\-\-|[^=!<>]=[^=!<>]).*\);",
-        "--",
-        "*.cpp",
-        "*.h",
-    ], "Assertions should not have side effects:")
-
     # Aborting the whole process is undesirable for RPC code. So nonfatal
     # checks should be used over assert. See: src/util/check.h
     # src/rpc/server.cpp is excluded from this check since it's mostly meta-code.
-    exit_code |= git_grep([
+    exit_code = git_grep([
         "-nE",
         r"\<(A|a)ss(ume|ert) *\(.*\);",
         "--",