Fix doctrees directory for the gettext builder (#122997)

Author: rffontenelle

Doc/Makefile

@@ -144,7 +144,7 @@ pydoc-topics: build
 
 .PHONY: gettext
 gettext: BUILDER = gettext
-gettext: SPHINXOPTS += '-d build/doctrees-gettext'
+gettext: SPHINXOPTS += -d build/doctrees-gettext
 gettext: build
 
 .PHONY: htmlview