Mention --quiet in --report option help

Author: sbidoul

news/11357.doc.rst

@@ -0,0 +1 @@
+Mention that --quiet must be used when writing the installation report to stdout.

src/pip/_internal/commands/install.py

@@ -263,7 +263,9 @@ def add_options(self) -> None:
                 "the provided requirements. "
                 "Can be used in combination with --dry-run and --ignore-installed "
                 "to 'resolve' the requirements. "
-                "When - is used as file name it writes to stdout."
+                "When - is used as file name it writes to stdout. "
+                "When writing to stdout, please combine with the --quiet option "
+                "to avoid mixing pip logging output with JSON output."
             ),
         )