Use a less sloppy check in remove_avoided_requirements

See pyodide/pyodide#5187. In that issue, the build
requires a package called `cmake-build-extension` but because we have `cmake` in
the list of requirements to avoid we drop it and it breaks the build.

This logic was introduced in pyodide/pyodide#2272 and
did not come up in the review. Surprisingly this is the first problem it has
caused. Let's see if this change breaks anything in Pyodide CI.

pyodide_build/pypabuild.py

@@ -118,7 +118,7 @@ def remove_avoided_requirements(
     for reqstr in list(requires):
         req = Requirement(reqstr)
         for avoid_name in set(avoided_requirements):
-            if avoid_name in req.name.lower():
+            if avoid_name == req.name.lower():
                 requires.remove(reqstr)
     return requires