Fixed typo.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>

HISTORY.rst

@@ -30,7 +30,7 @@ History
 0.4.6 (2020-10-12)
 ------------------
 
-* Use SPDX license identifier and set all files to GLP3+ to be consistent with license headers in the source files.
+* Use SPDX license identifier and set all files to GPL3+ to be consistent with license headers in the source files.
 * Excluded tests from being installed via 'pip install'.
 * Set development status to 'beta'.