documentation: Makefile: remove releases.rst in "make clean"

releases.rst is generated by the set_versions.py script

(From yocto-docs rev: 6a9aea1d4db67da095c81bc606f102aacfc436d2)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

documentation/Makefile

@@ -47,7 +47,7 @@ PNGs := $(foreach dir, $(IMAGEDIRS), $(patsubst %.svg,%.png,$(wildcard $(SOURCED
 	$(SVG2PNG) --export-filename=$@ $<
 
 clean:
-	@rm -rf $(BUILDDIR) $(PNGs) $(PDFs) poky.yaml sphinx-static/switchers.js
+	@rm -rf $(BUILDDIR) $(PNGs) $(PDFs) poky.yaml sphinx-static/switchers.js releases.rst
 
 stylecheck:
 	vale sync