Fix Bépo's BP_NNBS (narrow non-breaking space)

[precondition]

Description

diff --git a/quantum/keymap_extras/keymap_bepo.h b/quantum/keymap_extras/keymap_bepo.h
index 72d5b81f32..036aa128e7 100644
--- a/quantum/keymap_extras/keymap_bepo.h
+++ b/quantum/keymap_extras/keymap_bepo.h
@@ -237,4 +237,4 @@
 #define BP_DDAG S(ALGR(BP_H))    // ‡
 #define BP_FORD S(ALGR(BP_F))    // ª
 // Row 5
-#define BP_NNBS S(ALGR(BP_))     //   (narrow non-breaking space)
+#define BP_NNBS S(ALGR(KC_SPC))     //   (narrow non-breaking space)

BP_ isn't a valid macro.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).