gcc, g++: Clarify -Wall (#8647)

pages/common/g++.md

@@ -8,7 +8,7 @@
 
 `g++ {{path/to/source.cpp}} -o {{path/to/output_executable}}`
 
-- Display (almost) all errors and warnings:
+- Display common warnings:
 
 `g++ {{path/to/source.cpp}} -Wall -o {{path/to/output_executable}}`
 

pages/common/gcc.md

@@ -7,7 +7,7 @@
 
 `gcc {{path/to/source1.c path/to/source2.c ...}} -o {{path/to/output_executable}}`
 
-- Allow warnings, debug symbols in output:
+- Show common warnings, debug symbols in output:
 
 `gcc {{path/to/source.c}} -Wall -Og -o {{path/to/output_executable}}`