Improve f-string readability

Cannot reuse outer quote character in f-strings on Python 3.10,
syntax was added in Python 3.12.

Author: DimitriPapadopoulos

bench/ndarray/fancy_index.py

@@ -146,7 +146,7 @@ def timer(arr):
 plt.legend()
 plt.xticks(x-width, np.round(genuine_sizes, 2))
 plt.ylabel("Time (s)")
-plt.title(f"Fancy indexing {blosc2.__version__}, {NDIMS}D" +f"{" sparse" if SPARSE else ""}")
+plt.title(f"Fancy indexing {blosc2.__version__}, {NDIMS}D{' sparse' if SPARSE else ''}")
 plt.gca().set_yscale('log')
 plt.savefig(f'plots/fancyIdx{filename}.png', format="png")
 plt.show()

bench/ndarray/slice-expr-step.py

@@ -46,4 +46,4 @@ def _gitem():
 lab = 'LARGE' if LARGE_SLICE else 'SMALL'
 plt.title(f'{lab} slice w/steps, Linux Blosc2 {blosc2.__version__}')
 plt.legend([f'expr.slice({_slice}', f'expr[{_slice}]'])
-plt.savefig(f'sliceexpr_{lab}_Blosc{blosc2.__version__.replace('.','_')}.png', format="png")
+plt.savefig(f'sliceexpr_{lab}_Blosc{blosc2.__version__.replace(".","_")}.png', format="png")