Probe singleton patch

Followup to #16751

Marlin/src/module/probe.cpp

@@ -455,8 +455,8 @@ bool Probe::set_deployed(const bool deploy) {
  * @return true to indicate an error
  */
 
-#if HAS_HEATED_BED && ENABLED(WAIT_FOR_BED_HEATER)
-  PGM_P Probe::msg_wait_for_bed_heating[25] PROGMEM = "Wait for bed heating...\n";
+#if HAS_BED_PROBE && HAS_HEATED_BED && ENABLED(WAIT_FOR_BED_HEATER)
+  const char Probe::msg_wait_for_bed_heating[25] PROGMEM = "Wait for bed heating...\n";
 #endif
 
 bool Probe::move_to_z(const float z, const feedRate_t fr_mm_s) {

Marlin/src/module/probe.h

@@ -61,7 +61,7 @@ public:
       return probe_at_point(pos.x, pos.y, raise_after, verbose_level, probe_relative);
     }
     #if HAS_HEATED_BED && ENABLED(WAIT_FOR_BED_HEATER)
-      static PGM_P msg_wait_for_bed_heating[25];
+      static const char msg_wait_for_bed_heating[25];
     #endif
 
   #else