Mention breaking change regarding extra quotation marks around text strings in changelog v0.12.0 (#3462)

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>
Co-authored-by: Wei Ji <23487320+weiji14@users.noreply.github.com>

Author: 3 people

doc/changes.md

@@ -101,6 +101,7 @@
 
 ### Enhancements
 
+* **Breaking**: (Unneeded) extra double quotes around text strings (containing whitespaces) are now considered as part of the text string ([#3132](https://github.com/GenericMappingTools/pygmt/pull/3132), [#3457](https://github.com/GenericMappingTools/pygmt/issues/3457))
 * pygmt.project: Add 'output_type' parameter for output in pandas/numpy/file formats ([#3110](https://github.com/GenericMappingTools/pygmt/pull/3110))
 * pygmt.grdtrack: Add 'output_type' parameter for output in pandas/numpy/file formats ([#3106](https://github.com/GenericMappingTools/pygmt/pull/3106))
 * pygmt.blockm*: Add 'output_type' parameter for output in pandas/numpy/file formats ([#3103](https://github.com/GenericMappingTools/pygmt/pull/3103))